Domains page in Plesk GUI is loading too long, can appear as blank page or display the following error:
Unexpected token '<', "<html> <h"... is not valid JSON
UptimeRobot extension is installed.
- Log into Plesk.
- Disable the extension at Extensions > My Extensions > UptimeRobot > More > Disable
Note: Since the extension is developed by a 3rd-party consider contacting extension support at https://uptimerobot.com/contact/ so they could investigate this behavior from their side.