Upgrade from 11.0.9 to 11.5.3 is slow/slacked.
Upgrade procedure consist of many tasks which can take considerable time.
Check the upgrade log and clarify the status in log file: '
C:\pleskinstaller\autoinstaler3.log'. In '
autoinstaler3.log' file you can check the timestamps of the operations to monitor the upgrade process.
If Plesk runs several hundreds domains it can take several hours to process some upgrade tasks. For example repair task which upgrades statistics for all domains:
MSI (04) [2013-08-08 01:07:40.123]: Execute PHP script '"C:\Program Files (x86)\Parallels\Plesk\admin\bin\php.exe" -q -dauto_prepend_file="" -c "C:\Program Files (x86)\Parallels\Plesk\admin\php.ini" "C:\Program Files (x86)\Parallels\Plesk\admin\plib\cu\repair.php" --update-all-domains-web-stat'