Razer Atheris - BT problems

Hey there! I have a pretty new Razer Atheris and for some reason it stopped working on my Computer. First I connected it with my Surface Pro4 an a few weeks later to my Omen Laptop. A few days later the bluetooth connection stopped working. I even can't remove/unpair the mouse on both devices. I tried to remove it via Windows settings and via the device manager. And if I try to pair it again, it wont be found. I also tried the firmware update, but it says there is the new version installed. My girlfriends laptop is able to pair with my mouse. I think, cause it is the first time. It just works with the 2.4 GHz dongle on my devices. Pls help me, Ben