Monitoring in Plesk intermittently shows blank page with “An unexpected error occurred” message

Symptoms

• The error appears periodically in Plesk > Monitoring with 360 Monitoring configured:

  An unexpected error occurred

  or

  Request failed with status code 500

• The following record is frequently written to the log /var/log/plesk/panel.log:

  Http client exception: Read timed out after 20 seconds

Cause

Unstable network work that interrupts the connection between Plesk and 360 Monitoring.

Resolution

Check why the requests to 360 Monitoring take too much time with a network administrator.