Try logging into your server via ssh, su to root, and look for autoinstaller and rpm processes in both ps and in top. I f you have autoinstaller and rpm processes that are not in top, it is possible that they are zombie processes, or at least, no longer active.
Use
ps -ef | grep autoinstaller
and
ps -ef | grep rpm
to locate the processes
Use
top
to find the processes using the most resources on your server.
Autoinstaller calls rpm to find and update the plesk packages. The RPM database files, found in /var/lib/rpm as __db.nnn can become corrupted if a package install or update takes too long or is somehow interupted. This will cause the rpm processes to just hang around not doing anyting, which causes the autoinstaller to hang around not doing anything.
In your Plesk control panel, can you get to the Updater page?
Are there any messages there, near the top of the page?
Can you click on the available updates, in this case most likely 7.5.2, and will the page showing the component update status load, or does the control panel hang at that point? Can you use your browser's back button to get out of the "loading" message if it stalls?
Can you get to service managment or component info in the control panel?
We didn't have any error messages either. As a matter of fact, several packages installed successfully per the various /tmp logs. But the rpm databases had become corrupted as the pleks autoinstaller web site failed to respond serveral times.