Only certain number of users (less than licensed) are able to connect to Parallels Remote Application Server.
Network connection to Licensing Server has been lost.
Number of users that are able to connect Parallels Remote Application Server is equal to the number of users that were connected to Parallels Remote Application Server at the moment when connection to the Licensing Server has been lost.
Fix network connection to your Licensing Server.
If there is no possibility to fix your network connection, please set another site's Publishing Agent as Licensing Server:
Open Remote Application Server Console > Farm > Right click on secondary site > choose Set Site as Licensing Server > press Apply .
If there is no possibility to enter Remote Application Server Console please promote Backup Server to Master:
On the backup server open Console go to Farm > Backup Servers > right-click on the server > Promote Backup to Master