I get an erro of CTI OS server when I try to log in CAD as agent, I have 8961 (SIP phone) , any ideas?

hello,I have some 8945 phones, When I make a call to Side "A" outgoing thru VoIP calls complete successfully, but when I call to Site "B" calls are dropped.I guess something is missing in the Gateway in Site "B", I'm using SIP and H.323 trunks. pleas...