Dear Nicholas,
as mentionend in the title the "Test FTP Connection" button does not work properly since 1 or 2 weeks. It throws the following message:
AJAX Error
An error has occurred while waiting for an AJAX response:
AJAX Loading Error
HTTP Status: 0 ()
Internal status: timeout
XHR ReadyState: 4
Raw server response:
As you can see there is no status code and no server response. But the post processing works as expected. So the backup is stored correctly but the diagnosis button has some issue. For some reason this incident only occurs on my own virtual server that runs on Debian 11.6 and Plesk Obsidian 18.0.50. FTP and FTPS support is enabled, I cannot find any misconfiguration of the PHP module. In former versions of Akeeba Backup the button has worked as expected. Unfortunately I can't distinguish if it is a matter of the new Plesk, PHP or Akeeba Version.
It's just on my Plesk server, so it might be Plesk. But on other Plesk servers, this issue does not occur. So it might not be Plesk but a PHP misconfiguration. But I haven't change my PHP configuration in any way so there might be some issue on Akeeba.
What makes this error even worse is the case that when disabling "Report external IP in PASV mode" on my Synology FTP server, the Akeeba diagnosis button works well again but storing the backup on the ftp server does not work any more time.
Another problem for Akeeba could be that there are no "Write" permissions on the FTP root folder, only on the FTP subdirectory. That's why Akeeba has always reported that it could connect to the ftp server but could not store any test file. This behaviour is expected. Moreover there is no "Read" permission on the FTP subdirectory (only write files) because I don't want anybody who gains access to be able to read and download any backup archives. There is just a subdirecty you can write files into.
This ftp server configuration is quite a bit tricky for your Akeeba FTP diagnosis button but it has always shown the correct diagnosis on previous Akeeba versions. Unfortunately, I don't have any idea why this button is not working any more in Akeeba version 9.5.0 and exclusively on my own server.
Is there some code change that might be responsible for this? Do you have any idea?
Thank you very much for your help!