Okay understood, I did some quick tests and get similar results to yourself - paging works on 4.1.7 but not on 5.5.2 or 5.9.2. Noticed that one paging parameter was default set for expansion modules
https://documents.polycom.com/bundle/ucs-ag-5-8/page/r-ucs-ag-smart-paging-parameters.html - turned that parameter off but received same results. Put debug levels on the phone originating the page request and got a little more info from the diagnostic log.
Peter
0613170958|ptt |2|00| [PpsPttC]::ppsProcMsg(): MsgPpsCallDrop channel 26, reason 3
0613170958|ptt |2|00| [PpsPttC]::ppsProcMsg(): MsgPpsCallDrop Channel 26,Ptt AppId 0
0613170958|ptt |2|00| [PpsPttC]::ppsProcMsg(): MsgPpsCallDrop Mode=wlanModeStandby,Release Interval 650ms, Channel 26, Deleting the Ptt AppId 0
0613170958|ptt |2|00| [PpsPttC]::ppsProcMsg(): MsgPpsCallDrop Mode=wlanModeStandby,Release Interval 650ms Channel 26,After deleting the Ptt AppId 0
0613170958|net |4|00|rtosNetwork : rtosNetwDataSend() - can't send data. Connection with ID = 0 is not open.
0613170958|ptt |5|00|pttNetIoC::txPacket failed to send -2
0613170958|net |4|00|rtosNetwork : rtosNetwDataSend() - can't send data. Connection with ID = 0 is not open.
0613170958|ptt |5|00|pttNetIoC::txPacket failed to send -2
0613170958|ptt |1|00|[PpsPttChanC]: PTT channel=26, current state=EOT,event=Timeout, enter next state=Waiting
0613170958|ptt |1|00|[PpsPttChanC]: pttChannelC::enterWaiting numTries == [2]
0613171000|ptt |1|00|[PpsPttChanC]: PTT channel=26, current state=Waiting,event=Timeout, enter next state=Idle
0613171411|hw |5|00|Task ended without calling rtosTaskEnd() name=tTCPListen220