Found an interesting scenario that breaks your SBC MoH for call transfers. If you are using the Teams desktop client to answer calls, and you happen to put a call on hold and then resume it, you will then no longer receive re-invites from Teams when you press the Transfer or Consult then Transfer buttons for the rest of the call. This means your SBC has no idea that it is meant to start the local playback of its local MoH file for transfers. This will only happen if you put a call on hold and resume it before attempting transfers. If you attempt a transfer without using hold beforehand then there is no issue.
It seems that Teams no longer sends re-invites for calls that are placed on hold and resumed in the desktop client, but then it forgets that it's meant to do it if you want to transfer the calls afterwards. Not and issue on the Poly CCX 400 desk phones that I tested with as they still send re-invites for call hold and resume.
Has anyone else come across this and is there anyway to change the Teams behavior of no re-invites for Hold and Resume with the desktop clients?
I have tested this on 2 separate Teams tenants with SBCs from different vendors for validation.
