I drive a 2018 Mercedes CLA 250 and I currently have the 12/24/19 firmware installed. Oddly, I found with my car if I place the car in Reverse and keep it there it connects wirelessly. If the car is in Drive or Park it continually tries connecting and failing. Therefore, for my car I believe it’s a timing issue with the dongle timing out before it’s able to establish a wireless connection. Somehow placing the car in Reverse fixes the timing the issue???? I’ve sent tech support a message with the above info.