Yes, the headset button doesn't work for me now, in January 2021!
I bought this thing specifically because of the Teams certification....
It's even worse when it works for some and not for others - apparently MS really messed something up in a Teams update. I think Jabra should take more active care of it, as they advertise it that way :-(

Response from Jabra Support: "Jabra R&D has recently identified the loss of headset call control when using MS Teams. After investigation, all indications are that it is a MS Teams behaviour and unfortunately there is not much we can do from our side. The problem does not only affect Jabra users, but also our competitors. We advise you to regularly check for the latest MS Teams updates as a solution could appear at any time."

But it works quite well. I have to admit, not 100%, but most of the time it works without problems.