Errors & troubleshooting

The server refuses the file. Folders should be 755 and files 644; also check your .htaccess for blocking rules.

PHP stopped with an error it isn't allowed to show. Turn on error reporting or open your server's error log to see the message.

Use SMTP: enter your mail provider's details in Global Configuration → Server → Mail, use an address on your own domain as sender, and click Send Test Mail.

Usually an extension that isn't ready for the new version. Turn on error reporting to see which one, then disable it.

System → Global Configuration → Server → Error Reporting: Maximum. If the admin is down, set $error_reporting = 'maximum' in configuration.php.

In the administrator/logs folder (set under Global Configuration → System). PHP errors go to your server's error log, which your hosting panel shows.

Clear the cache in System → Clear Cache, then reload the page with Ctrl/Cmd + Shift + R.

The page behind it is unpublished, trashed, or set to an access level you don't have. Also check the trash for an item with the same alias.

Your session expired. Reload the page and try again; if it keeps happening, raise Session Lifetime in Global Configuration.

configuration.php is read-only. Set it to 644 with your file manager, save the settings, then set it back to 444 if you like.

The log folder path is wrong, often after a move. Set the right path in Global Configuration → System → Path to Log Folder.

Set Path to Temp Folder in Global Configuration → Server to your site's tmp folder, and make sure it is writable (755).

Joomla can't write to its folders. Check the tmp path and folder permissions, or that the zip isn't bigger than your upload limit.