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Sorry to hear you’re facing problems 
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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): 25.0.0.18
Operating system and version (eg, Ubuntu 20.04): nethserver 7.9.2009
Apache or nginx version (eg, Apache 2.4.25): 2.4.6
PHP version (eg, 7.4): 8.0.23
The issue you are facing:
Downgrading is not supported and is likely to cause unpredictable issues (from 25.0.0.18 to 24.0.7.1)
Is this the first time you’ve seen this error? (Y/N): Y
Steps to replicate it:
- Upgraded to 25.0.0.18
- Haven’t touched upgrade since the upgrade
- Auto updater is on
The output of your Nextcloud log in Admin > Logging:
Cant access anything, OCC not working just throwing the Downgrading is not supported and is likely to cause unpredictable issues (from 25.0.0.18 to 24.0.7.1)
The output of your config.php file in /path/to/nextcloud (make sure you remove any identifiable information!):
<?php
$CONFIG = array (
'instanceid' => 'REDACTED',
'passwordsalt' => 'REDACTED',
'secret' => 'REDACTED',
'datadirectory' => '/mydata/DATA/',
'dbtype' => 'sqlite3',
'version' => '25.0.0.18',
'overwrite.cli.url' => 'https://myip/nextcloud',
'installed' => true,
'updater.release.channel' => 'stable',
'maintenance' => false,
'memcache.local' => '\\OC\\Memcache\\APCu',
'logfile' => '/var/lib/nethserver/nextcloud/nextcloud.log',
'mail_smtpmode' => 'smtp',
'mail_smtpsecure' => '',
'mail_smtpauthtype' => 'LOGIN',
'mail_from_address' => 'no-reply',
'mail_domain' => 'homenet.dom',
'mail_smtphost' => 'localhost',
'mail_smtpport' => '25',
'loglevel' => 2,
'theme' => '',
'app_install_overwrite' =>
array (
0 => 'dicomviewer',
),
'dbhost' => 'localhost:/run/rh-mariadb105-mariadb/nextcloud-mysql.sock',
'mysql.utf8mb4' => true,
'updatechecker' => false,
'check_for_working_wellknown_setup' => false,
'trusted_domains' =>
array (
0 => 'localhost',
1 => 'mydomain',
2 => 'my ip',
),
);
The output of your Apache/nginx/system log in /var/log/____:
PASTE HERE
PASTE HERE
Output errors in nextcloud.log in /var/www/ or as admin user in top right menu, filtering for errors. Use a pastebin service if necessary.
{"reqId":"Y2kXYgT7LDlsrA7A7fwlrQAAAEc","level":4,"time":"2022-11-07T14:34:10+00:00","remoteAddr":"myIP","user":"PK1","app":"webdav","method":"PROPFIND","url":"/nextcloud/remote.php/dav/files/PK1/","message":"OCP\\HintException: Downgrading is not supported and is likely to cause unpredictable issues (from 25.0.0.18 to 24.0.7.1)","userAgent":"Mozilla/5.0 (Windows) mirall/3.4.0stable-Win64 (build 20211129) (Nextcloud, windows-10.0.19044 ClientArchitecture: x86_64 OsArchitecture: x86_64)","version":"25.0.0.18","exception":{"Exception":"Sabre\\DAV\\Exception\\ServiceUnavailable","Message":"OCP\\HintException: Downgrading is not supported and is likely to cause unpredictable issues (from 25.0.0.18 to 24.0.7.1)","Code":0,"Trace":[{"file":"/usr/share/nextcloud/3rdparty/sabre/event/lib/WildcardEmitterTrait.php","line":89,"function":"{closure}","args":["*** sensitive parameters replaced ***"]},{"file":"/usr/share/nextcloud/3rdparty/sabre/dav/lib/DAV/Server.php","line":456,"function":"emit","class":"Sabre\\DAV\\Server","type":"->"},{"file":"/usr/share/nextcloud/3rdparty/sabre/dav/lib/DAV/Server.php","line":253,"function":"invokeMethod","class":"Sabre\\DAV\\Server","type":"->"},{"file":"/usr/share/nextcloud/3rdparty/sabre/dav/lib/DAV/Server.php","line":321,"function":"start","class":"Sabre\\DAV\\Server","type":"->"},{"file":"/usr/share/nextcloud/remote.php","line":76,"function":"exec","class":"Sabre\\DAV\\Server","type":"->"},{"file":"/usr/share/nextcloud/remote.php","line":172,"function":"handleException"}],"File":"/usr/share/nextcloud/remote.php","Line":74,"CustomMessage":"--"}}
and I found two things in their FAQ, which might have caused your issue: