Cannot delete WordPress plugin in WordPress Toolkit

Applicable to:

Cannot delete WordPress plugin in WordPress Toolkit.

There are no any relevant errors in log files.

proc_open() was disabled in php.ini for PHP version of the website.

Determine what version of PHP is in use: Plesk > domains > example.com > PHP Settings > PHP support .
Go to Plesk > Tools&Settings > PHP Settings > PHP version and handler for the domain > php.ini .
In opened editor search for disabled_functions line and remove proc_open() from it.