Sorry not sure I follow, "wont detach". You have the detach button in the top right hand corner, assuming it a SB3 model. Does it not flash green when pressed.
The other method which work for me to bring back the GPU was a cold boot. ( Press and hold down the power button until the Surface shuts down and restarts and you see the Windows logo screen ( approx 20 seconds ), "then release the power button". Check device manager or task manager.
Update, If it doesnt detach as the button doesnt work, I found this manual method below. I would be very careful however , ideally something non metallic.
Attempt at your own risk.
\[PSA\] Surface Book keyboard manual release | Microsoft Surface Forums