Using overwatch, I am unable to button map scroll right to melee or any action for that matter. Is there a way to fix this?
Hey there my friend,
In many cases, we have found the best answer for unbind-able keys on gaming hardware like this is to bind it in the software for the device.
Many times these have profiles, ones you can freely change between or even ones that are dependent on a game being open. Binding the right scroll to something like ‘Shift + L’ and then binding the action to that in game should work.
I hope this helps my friend. In the end, we do not support gaming hardware binds like this. I hope as a gamer too, that this info helps. 
/Nathardrick