What IPs should be opened in the firewall to connect a server to Plesk 360?
Plesk 360 using the below IP addresses, please make sure to allow connections from these IPs:
Additionally, 360 monitoring uses the below IPs to access server/websites: https://monitoring.platform360.io/whitelist.php
The instructions on how to manage the rules by using Plesk Firewall might be found here.
Note: If there is an external firewall outside the server the rules should be adjusted there.