When clicking on Updates and Upgrades in Plesk, the page prompts for a root password or does not open at all with one of the following error messages in a web-browser:
The connection has timed out
This site can’t be reached
When starting Plesk Installer in a command-line interface, the following message is shown:
BUSY: Update operation was locked by another update process.
Error: Unable to start Plesk Installer. The following error has occurred: Installation could not be started: another installation procedure is currently running.
A Plesk Installer process is running on the server already, but only one Plesk Installer process can be launched at a time.
Terminate active Plesk Installer processes:
Note: Before applying the solution below, make sure that other users on the Plesk server are not using Plesk Installer.
Connect to the Plesk server via SSH (Linux) / RDP (Windows Server)
Stop Plesk Installer processes (on Windows Server, use a command prompt as Administrator):
# plesk installer stop