Hello the nextcloud world ! 
I installed NextCloud on a new scaleway instance following this tutorial:
(I didn’t use Let’s Encrypt, but a certificate of my own with nextcloud.enable-https custom).
The problem: In admin/overview I have the message: “This server has no working Internet connection: Multiple endpoints could not be reached.”
However, the server has access to Internet correctly: I can ping on www.google.com and on all other addresses. A nslookup also works and a curl www.google.com returns a web page (same with curl www.nextcloud.com, curl www.edri.org or curl www.startpage.com).
Thanks to all of you for the help.
Nextcloud version: 15.0.5.3
Operating system: Ubuntu Bionic Beaver (18.04 LTS)
PHP version: 7.2.16
The output of Admin > Logging:
Error internet_connection_check GuzzleHttp\Exception\ConnectException: cURL error 6: Could not resolve host: www.edri.org (see http://curl.haxx.se/libcurl/c/libcurl-errors.html) 2019-04-05T14:16:34+0200
Error internet_connection_check GuzzleHttp\Exception\ConnectException: cURL error 6: Could not resolve host: www.eff.org (see http://curl.haxx.se/libcurl/c/libcurl-errors.html) 2019-04-05T14:16:34+0200
Error internet_connection_check GuzzleHttp\Exception\ConnectException: cURL error 6: Could not resolve host: www.startpage.com (see http://curl.haxx.se/libcurl/c/libcurl-errors.html) 2019-04-05T14:16:34+0200
Error internet_connection_check GuzzleHttp\Exception\ConnectException: cURL error 6: Could not resolve host: www.nextcloud.com (see http://curl.haxx.se/libcurl/c/libcurl-errors.html) 2019-04-05T14:16:34+0200
…
The output of config.php file in /var/snap/nextcloud/12387/nextcloud/config:
<?php ,b=window.innerHeight;if(!a||!b){var c=window.document,d="CSS1Compat"==c.comp
$CONFIG = array ( ).call(this);})();(function(){var u='/xjs/_/js/k\x3dxjs.hp.en.ZdeC6FttH4A.O/m
'apps_paths' => ick&&google.tick("load","xjsls");document.body.appendChild(a)},0);})();(funct
array (
0 => ,\x22dh\x22:true,\x22dhqt\x22:true,\x22ds\x22:\x22\x22,\x22ffql\x22:\x22fr\x2
array ( orthographe :\x22,\x22lcky\x22:\x22J\\u0026#39;ai de la chance\x22,\x22lml\x2
'path' => '/snap/nextcloud/current/htdocs/apps', \u003E.\x22,\x22psrl\x22:\x22Supprimer\x22,\x22sbit\x22:\x22Recherche par ima
'url' => '/apps', dri.org
'writable' => false,
),
1 =>
array (
'path' => '/var/snap/nextcloud/current/nextcloud/extra-apps',
'url' => '/extra-apps',
'writable' => true,
),
),
'supportedDatabases' =>
array (
0 => 'mysql',
),
'memcache.locking' => '\\OC\\Memcache\\Redis',
'memcache.local' => '\\OC\\Memcache\\Redis',
'redis' =>
array (
'host' => '/tmp/sockets/redis.sock',
'port' => 0,
),
'passwordsalt' => '***',
'secret' => '***',
'trusted_domains' =>
array (
0 => 'localhost',
1 => '***',
),
'datadirectory' => '/var/snap/nextcloud/common/nextcloud/data',
'dbtype' => 'mysql',
'version' => '15.0.5.3',
'overwrite.cli.url' => 'http://localhost',
'dbname' => 'nextcloud',
'dbhost' => 'localhost:/tmp/sockets/mysql.sock',
'dbport' => '',
'dbtableprefix' => 'oc_',
'mysql.utf8mb4' => true,
'dbuser' => 'nextcloud',
'dbpassword' => '***',
'installed' => true,
'instanceid' => '***',
'has_internet_connection' => true,
'maintenance' => false,
);