Teams transferring PBX call through Teams


So if I try to transfer the PBX call to the Teams username, call rings once and says “transfer failed”.
If I hit the drop down after searching for the Teams user, and transfer to the number it works…

I hope this makes sense. Is this an outbound route issue? The issue is that I cannot transfer to the username, but I can hit the drop down and the transfer is successful when transferring directly to number…