Sorry for my bad English!
Support intro
Sorry to hear you’re facing problems 
help.nextcloud.com is for home/non-enterprise users. If you’re running a business, paid support can be accessed via portal.nextcloud.com where we can ensure your business keeps running smoothly.
In order to help you as quickly as possible, before clicking Create Topic please provide as much of the below as you can. Feel free to use a pastebin service for logs, otherwise either indent short log examples with four spaces:
example
Or for longer, use three backticks above and below the code snippet:
longer
example
here
Some or all of the below information will be requested if it isn’t supplied; for fastest response please provide as much as you can 
Nextcloud version (eg, 20.0.5): Nextcloud 22.0.0 beta 4
Operating system and version (eg, Ubuntu 20.04): Ubuntu 20.04.2 LTS
Apache or nginx version (eg, Apache 2.4.25): Apache/2.4.41
PHP version (eg, 7.4): PHP 7.4.3 (cli) (built: Jul 5 2021 15:13:35) ( NTS )
The issue you are facing:
Is this the first time you’ve seen this error? (Y/N): Y
Steps to replicate it:
- Log to my account
- Show notification
- The update server could not be reached since 35 days to check for new updates.
The output of your Nextcloud log in Admin > Logging:
Error internet_connection_check Cannot connect to: www.nextcloud.com 2021-07-21T08:57:35+0300
Error internet_connection_check Cannot connect to: www.nextcloud.com 2021-07-21T08:57:31+0300
The output of your config.php file in /path/to/nextcloud (make sure you remove any identifiable information!):
<?php
$CONFIG = array (
'instanceid' => '****************',
'passwordsalt' => '******************************/',
'secret' => *************************************',
'trusted_domains' =>
array (
0 => '********************',
),
'datadirectory' => '/var/nclouddata',
'dbtype' => 'mysql',
'version' => '22.0.0.7',
'overwrite.cli.url' => '******************************',
'dbname' => 'ncloud',
'dbhost' => '192.168.1.111:3306',
'dbport' => '',
'dbtableprefix' => 'oc_',
'mysql.utf8mb4' => true,
'dbuser' => '***********************',
'dbpassword' => '*******************',
'installed' => true,
'memcache.local' => '\\OC\\Memcache\\APCu',
'twofactor_enforced' => 'true',
'default_phone_region' => 'RU',
'twofactor_enforced_groups' =>
array (
0 => 'admin',
),
'twofactor_enforced_excluded_groups' =>
array (
),
'maintenance' => false,
'theme' => '',
'log_type' => 'owncloud',
'logfile' => '/var/log/nextcloud.log',
'loglevel' => '2',
'mail_smtpmode' => 'smtp',
'mail_sendmailmode' => 'pipe',
'mail_from_address' => '***********************',
'mail_domain' => '************************',
'mail_smtpauthtype' => 'LOGIN',
'mail_smtpauth' => 1,
'mail_smtphost' => '*************************',
'mail_smtpport' => '***',
'mail_smtpname' => '***************************',
'mail_smtppassword' => '***************************',
'mail_smtpsecure' => 'tls',
'mail_smtpstreamoptions' =>
array (
'ssl' =>
array (
'allow_self_signed' => true,
'verify_peer' => false,
'verify_peer_name' => false,
),
),
'updater.release.channel' => 'beta',
'app_install_overwrite' =>
array (
0 => 'dashboard',
1 => 'terms_of_service',
2 => 'music',
3 => 'checksum',
4 => 'folderplayer',
5 => 'bruteforcesettings',
6 => 'files_accesscontrol',
7 => 'twofactor_totp',
8 => 'groupfolders',
),
);
The output of your Apache/nginx/system log in /var/log/____:
Handler/CurlFactory.php","Line":210,"CustomMessage":"Cannot connect to: www.nextcloud.com"}}
{"reqId":"yHoh4ISFmspjeKvn9NE3","level":3,"time":"2021-07-21T05:57:35+00:00","remoteAddr":"80.246.209.59","user":"DimmKo","app":"internet_connection_check","method":"GET","url":"/index.php/settings/ajax/checksetup","message":"Cannot connect to: www.nextcloud.com","userAgent":"Mozilla/5.0 (Windows NT 6.3; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/91.0.4472.166 Safari/537.36","version":"22.0.0.7","exception":{"Exception":"GuzzleHttp\\Exception\\ConnectException","Message":"cURL error 7: (see https://curl.haxx.se/libcurl/c/libcurl-errors.html) for http://www.nextcloud.com/","Code":0,"Trace":[{"file":"/var/www/nextcloud/3rdparty/guzzlehttp/guzzle/src/Handler/CurlFactory.php","line":158,"function":"createRejection","class":"GuzzleHttp\\Handler\\CurlFactory","type":"::"},{"file":"/var/www/nextcloud/3rdparty/guzzlehttp/guzzle/src/Handler/CurlFactory.php","line":110,"function":"finishError","class":"GuzzleHttp\\Handler\\CurlFactory","type":"::"},{"file":"/var/www/nextcloud/3rdparty/guzzlehttp/guzzle/src/Handler/CurlHandler.php","line":47,"function":"finish","class":"GuzzleHttp\\Handler\\CurlFactory","type":"::"},{"file":"/var/www/nextcloud/lib/private/Http/Client/DnsPinMiddleware.php","line":124,"function":"__invoke","class":"GuzzleHttp\\Handler\\CurlHandler","type":"->"},{"file":"/var/www/nextcloud/3rdparty/guzzlehttp/guzzle/src/PrepareBodyMiddleware.php","line":35,"function":"OC\\Http\\Client\\{closure}","class":"OC\\Http\\Client\\DnsPinMiddleware","type":"->","args":["*** sensitive parameters replaced ***"]},{"file":"/var/www/nextcloud/3rdparty/guzzlehttp/guzzle/src/Middleware.php","line":31,"function":"__invoke","class":"GuzzleHttp\\PrepareBodyMiddleware","type":"->"},{"file":"/var/www/nextcloud/3rdparty/guzzlehttp/guzzle/src/RedirectMiddleware.php","line":71,"function":"GuzzleHttp\\{closure}","class":"GuzzleHttp\\Middleware","type":"::","args":["*** sensitive parameters replaced ***"]},{"file":"/var/www/nextcloud/3rdparty/guzzlehttp/guzzle/src/Middleware.php","line":63,"function":"__invoke","class":"GuzzleHttp\\RedirectMiddleware","type":"->"},{"file":"/var/www/nextcloud/3rdparty/guzzlehttp/guzzle/src/HandlerStack.php","line":75,"function":"GuzzleHttp\\{closure}","class":"GuzzleHttp\\Middleware","type":"::","args":["*** sensitive parameters replaced ***"]},{"file":"/var/www/nextcloud/3rdparty/guzzlehttp/guzzle/src/Client.php","line":331,"function":"__invoke","class":"GuzzleHttp\\HandlerStack","type":"->"},{"file":"/var/www/nextcloud/3rdparty/guzzlehttp/guzzle/src/Client.php","line":168,"function":"transfer","class":"GuzzleHttp\\Client","type":"->"},{"file":"/var/www/nextcloud/3rdparty/guzzlehttp/guzzle/src/Client.php","line":187,"function":"requestAsync","class":"GuzzleHttp\\Client","type":"->"},{"file":"/var/www/nextcloud/lib/private/Http/Client/Client.php","line":223,"function":"request","class":"GuzzleHttp\\Client","type":"->"},{"file":"/var/www/nextcloud/apps/settings/lib/Controller/CheckSetupController.php","line":179,"function":"get","class":"OC\\Http\\Client\\Client","type":"->"},{"file":"/var/www/nextcloud/apps/settings/lib/Controller/CheckSetupController.php","line":162,"function":"isSiteReachable","class":"OCA\\Settings\\Controller\\CheckSetupController","type":"->"},{"file":"/var/www/nextcloud/apps/settings/lib/Controller/CheckSetupController.php","line":738,"function":"hasInternetConnectivityProblems","class":"OCA\\Settings\\Controller\\CheckSetupController","type":"->"},{"file":"/var/www/nextcloud/lib/private/AppFramework/Http/Dispatcher.php","line":217,"function":"check","class":"OCA\\Settings\\Controller\\CheckSetupController","type":"->"},{"file":"/var/www/nextcloud/lib/private/AppFramework/Http/Dispatcher.php","line":126,"function":"executeController","class":"OC\\AppFramework\\Http\\Dispatcher","type":"->"},{"file":"/var/www/nextcloud/lib/private/AppFramework/App.php","line":156,"function":"dispatch","class":"OC\\AppFramework\\Http\\Dispatcher","type":"->"},{"file":"/var/www/nextcloud/lib/private/Route/Router.php","line":303,"function":"main","class":"OC\\AppFramework\\App","type":"::"},{"file":"/var/www/nextcloud/lib/base.php","line":998,"function":"match","class":"OC\\Route\\Router","type":"->"},{"file":"/var/www/nextcloud/index.php","line":36,"function":"handleRequest","class":"OC","type":"::"}],"File":"/var/www/nextcloud/3rdparty/guzzlehttp/guzzle/src/Handler/CurlFactory.php","Line":210,"CustomMessage":"Cannot connect to: www.nextcloud.com"}}
From my console
dig www.nextcloud.com
; <<>> DiG 9.16.1-Ubuntu <<>> www.nextcloud.com
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 58558
;; flags: qr rd ra; QUERY: 1, ANSWER: 1, AUTHORITY: 0, ADDITIONAL: 1
;; OPT PSEUDOSECTION:
; EDNS: version: 0, flags:; udp: 65494
;; QUESTION SECTION:
;www.nextcloud.com. IN A
;; ANSWER SECTION:
www.nextcloud.com. 1056 IN A 95.217.53.153
;; Query time: 0 msec
;; SERVER: 127.0.0.53#53(127.0.0.53)
;; WHEN: Wed Jul 21 09:12:36 MSK 2021
;; MSG SIZE rcvd: 62
ping to hosy
PING www.nextcloud.com (95.217.53.153) 56(84) bytes of data.
64 bytes from nextcloud.com (95.217.53.153): icmp_seq=1 ttl=56 time=18.4 ms
64 bytes from nextcloud.com (95.217.53.153): icmp_seq=2 ttl=56 time=18.3 ms
64 bytes from nextcloud.com (95.217.53.153): icmp_seq=3 ttl=56 time=18.3 ms
64 bytes from nextcloud.com (95.217.53.153): icmp_seq=4 ttl=56 time=18.4 ms
64 bytes from nextcloud.com (95.217.53.153): icmp_seq=5 ttl=56 time=18.3 ms
64 bytes from nextcloud.com (95.217.53.153): icmp_seq=6 ttl=56 time=18.3 ms
64 bytes from nextcloud.com (95.217.53.153): icmp_seq=7 ttl=56 time=18.4 ms
64 bytes from nextcloud.com (95.217.53.153): icmp_seq=8 ttl=56 time=18.3 ms
64 bytes from nextcloud.com (95.217.53.153): icmp_seq=9 ttl=56 time=18.4 ms
64 bytes from nextcloud.com (95.217.53.153): icmp_seq=10 ttl=56 time=18.3 ms
64 bytes from nextcloud.com (95.217.53.153): icmp_seq=11 ttl=56 time=18.3 ms
64 bytes from nextcloud.com (95.217.53.153): icmp_seq=12 ttl=56 time=18.4 ms
64 bytes from nextcloud.com (95.217.53.153): icmp_seq=13 ttl=56 time=18.4 ms
64 bytes from nextcloud.com (95.217.53.153): icmp_seq=14 ttl=56 time=18.4 ms
64 bytes from nextcloud.com (95.217.53.153): icmp_seq=15 ttl=56 time=18.4 ms
64 bytes from nextcloud.com (95.217.53.153): icmp_seq=16 ttl=56 time=18.4 ms
64 bytes from nextcloud.com (95.217.53.153): icmp_seq=17 ttl=56 time=18.4 ms
64 bytes from nextcloud.com (95.217.53.153): icmp_seq=18 ttl=56 time=18.5 ms
64 bytes from nextcloud.com (95.217.53.153): icmp_seq=19 ttl=56 time=18.3 ms
64 bytes from nextcloud.com (95.217.53.153): icmp_seq=20 ttl=56 time=18.2 ms
64 bytes from nextcloud.com (95.217.53.153): icmp_seq=21 ttl=56 time=18.3 ms
^C
--- www.nextcloud.com ping statistics ---
21 packets transmitted, 21 received, 0% packet loss, time 20028ms
rtt min/avg/max/mdev = 18.240/18.361/18.505/0.064 ms