Check that the user is explicitly logged in to that specific queue. The button on top in the Global login, but it does not mean that you are automatically logged into individual queues: https://www.3cx.com/docs/pbx-queue-status/#h.ivks9coc1qu5
Thanks for your replay!
the problem is not logging into the queue, but answering the phone. The app will ring and when i press the button to accept the call it doesn't work.
Have you tried to remove the app completely?
I had the same issue after some updates for 3CX a few weeks ago where my client couldnt pick up calls anymore with the app on android and osx.
Completely removed the account from the app.
Completely removed the app from the phones.
Reinstalled it 3CX app
Send new welcome message
And provision via QR
Test again
I am having the same issues on 16.3 and 16.4.1. I also have an issue where I need to close and open the app when connected via wifi to the same network as the server for my status to go green.