Brightness keys not working on surface 3 type cover

I noticed this yesterday and I have been unable to resolve it. The brightness keys on my surface 3 type cover don't control screen brightness anymore. Neither the increase brightness key nor the decrease brightness key

I've tried attaching and reattaching the type cover but no difference
I've tried a few restarts bu nothing
I've tried reinstalling the drivers but still the same

I don't believe the physical keys have an issue - since I'm able to get the function key working

Other keys work such as the disable audio, type cover backlit lights etc

Any ideas?

I'm on release preview of windows 10

I created a new user account and transferred all my data to the new account - and now the brightness keys are working again