A user is being logged out from Plesk periodically when navigating between pages in Plesk interface.
Plesk redirects to the login page after a successful login attempt.
User's IP address is changed during a Plesk session. This may happen if user's IP address is dynamic or the domain/hostname which is used as a URL for Plesk is behind Cloudflare.
By default, Plesk does not allow IP address changes during a single session.
Allow IP address changes during a single session:
Log in to Plesk (use the server IP address if it is not possible to log in using the hostname).
Go to Tools & Settings > Session Idle Time and enable the option Allow IP address changes during a single session.
Click OK to apply the changes.