- Plesk Onyx for Linux
- The Comodo Modsecurity rules were activated at Tools & Settings > Web Application Firewall > Change Rule Set with valid Comodo subscription credentials.
- The confusing message "Enter another username and password" appeared:
This is Plesk bug with ID PPP-43570 which will be fixed in future Plesk versions.
Until the bug is fixed, check that Comodo rules are activated at Tools & Settings > Web Application Firewall: