i have problems with incoming calls from other ip phones to 8851 cisco ip phone with Newrock OM series ip pbx as the main pbx server!!
outgoing calls from my 8851 ip phone are ok!!
i tried reinstalling firmware but that wasn't helpful!
i'm currently using sip 88xx v.12 that released on sep,2019
one thing I found out about newrock is that it is sending the sip packets but will get no response from 8851
anything might be helpful!