Unable to open the "Updates and Upgrades" page or start Plesk Installer in CLI: Update operation was locked by another update process

Plesk for Windows Plesk for Linux kb: technical ABT: Group A FR:PPM-2446

Applicable to:

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

ERR_TIMED_OUT
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

For Plesk Onyx, apply the following steps:

For Plesk on Linux

Connect to the Plesk server via SSH
Find the PIDs of Plesk Installer processes:

# ps aux | grep install | grep -v grep

root 12345 1.5 0.8 136856 18280 ? S 20:43 0:00 /var/cache/parallels_installer/parallels_installer_CentOS_7_x86_64_3.21.3 --service-mode --enable-xml-output --ssl-cert /usr/local/psa/admin/conf/httpsd.pem --branch release,stable --web-interface --with-ssl --disable-browser
root 12346 0.0 0.1 109776 2808 ? S 20:43 0:00 /var/cache/parallels_installer/parallels_installer_CentOS_7_x86_64_3.21.3 --service-mode --enable-xml-output --ssl-cert /usr/local/psa/admin/conf/httpsd.pem --branch release,stable --web-interface --with-ssl --disable-browser
Kill found processes using the command below. Replace 12345 12346 with actual PIDs from the step above:

# kill -9 12345 12346
Remove the /tmp/psa-installer.lock file, if it exists
Start Plesk Installer

For Plesk on Windows Server

Apply one of the following solutions:

Terminate Plesk Installer processes using a command prompt:
1. Connect to the Plesk server via RDP
2. Start a command prompt
3. Find the PID of a Plesk Installer process:
  
  wmic process where "caption like '%installer%'" get processId,caption
  Caption ProcessId
  parallels_installer_Microsoft_10.0_x86_64_3.22.12.exe **6444
  **Caption ProcessIdai.exe 6444
4. Kill the process using its PID:
  
  taskkill /PID 6444 /F
5. Kill the ai.exe process:
  
  taskkill /FI "IMAGENAME eq ai.exe" /F
Terminate Plesk Installer processes using Windows Task Manager
1. Open Task Manager (Open Windows Start > type "Task Manager")
2. Right-click on each existing "Plesk Installer" process and click End Task:
  
  Note: Plesk Installer processes can have one of the following names depending on Plesk version: Plesk Installer, ai.exe, parallels-installer.exe or plesk-installer.exe.