Yealink MP56 device - MS Teams Join Button

[Dan.M]

I've submitted a support request however I am wondering if any others have ran into this issue and may have some insight. This is a MS Teams call join feature as described in article link below. If you have MS Teams on multiple devices this join button appears, so for example I have a desktop pc, a laptop, a cell phone and a Yealink mp56 teams desk phone.
When I call my phone number all my devices give me option to answer call. Once I answer my other devices have the join button displayed. The Yealink desk phone does not. It used to but now has stopped, on all phones. We have a few hundred deployed.

MS Article: https://support.microsoft.com/en-gb/offi...ct%20Join.