Scheduled Tasks Shell Setting – Set the default shell for scheduled tasks

To set the shell that will be used to run all “Run a Command” scheduled
tasks by default, go to Tools & Settings > Scheduled Tasks >
Settings and select the desired shell from the menu.

Alternatively, you can log in to the server via ssh and run the
following command:

plesk bin server_pref -u -crontab-secure-shell "<shell>"

Where <shell> is the desired shell. For example:

plesk bin server_pref -u -crontab-secure-shell "/bin/bash"