Parallels Plesk hanging on login

I recently came across a strange problem when setting up a new Windows Server running Parallels Plesk 12.

Everything was working fine to being with, and then suddenly Parallels Plesk started behaving strangely. I would select some items in a list and press remove and they would be greyed out as if the AJAX had fired in the background, but they wouldn’t be removed from the list until refreshing the page.

Wondering if this was some kind of browser problem as I was using Apple’s Safari, I fired up Mozilla’s Firefox but was somewhat surprised that I couldn’t get past the login screen.

The login page loads, but once I’d entered the username and password and pressed “Log In”, the page would just hang, loading indefinitely until it eventually times out.

The CPU and memory usage on the server were fine. The services were all running correctly. What’s going on?

After a quick look in “C:\Program Files (x86)\Parallels\Plesk\admin\logs\php_error”, it was pretty obvious that the recently installed Parallels Panel Mobile Center extension wasn’t working properly, as there were lots of errors about being unable to access files in “C:\Program Files (x86)\Parallels\Plesk\var\modules\plesk-mobile”.

Deleting the “C:\Program Files (x86)\Parallels\Plesk\var\modules\plesk-mobile” folder at least allowed me to log back in to the Parallels Plesk control panel, however the Parallels Panel Mobile Center extension couldn’t be removed.

After a bit of digging, it seems that the permissions on “C:\Program Files (x86)\Parallels\Plesk\var\modules\” aren’t set correctly out of the box and the “psaadm” user needed to be given write access to this folder in order to create or remove the files and folders for extensions when they are installed/uninstalled.

Once the permissions had been corrected, I was able to remove and then reinstall the Parallels Panel Mobile Center extension successfully.