NetScaler ns.log "Failed to process setclient for id , user due to "<license limit reached>""

Customer finds following message in /var/log/ns.log, which indicates some gateway users failed to login: Aug 14 09:17:01 x.x.x.x 08/14/2023:01:17:01 GMT xxxxxxx 0-PPE-5 : default SSLVPN Message 503230 0 : "Failed to process setclient for id , user due to " "...