Avaya >>UCM62xx >> 3CX = calls dropped


Dear forum,

We have a SIP peer between and Avaya IP 500 and a UCM62xx, and then we have a SIP registered trunk between that UCM and 3CX (I know, it is a long story to explain…)

We are able to call from Avaya to 3CX passing through the UCM, but the minute we answered the call on the 3CX, that call is dropped on the Avaya, it looks like the UCM, instead of passing the call forward and becoming a link between Avaya and 3CX, it takes the call and pass it to 3CX but drops it from the Avaya

Is there a way to prevent this from happening? We need the Avaya PBX to call the 3CX by having the call re-directed to the UCM first

Any adivse will be greatly appreciated!

Thank you