Having a similar issue. By default all of the key assignments are 'none', except for Left/Right/Middle Click, and DPI Up/Down, which work fine. Soon as I bind them to ANYTHING else, they stop working entirely.
For example, if I leave everything as default, I can use the left/right mouse buttons like normal. If I rebind one of them to, for example, the 'A' key, it stops working. As soon as I bind any function to any button, that button stops working. Not just the side buttons, but all buttons. To clarify, as soon as I press 'Reset to Default' on any given keybind, it starts working again. If I rebind it to something else, it stops working.
Here is my current situation:
Using Corsair Scimitar RGB Mouse. Upgraded to 2.01 firmware, which caused it to stop working. Found this thread, rolled back to 1.06 firmware, but it is still not working. Using CUE 1.15.36 if that matters. The CUE software seems to be fine, and the connection to the mouse seems fine. I can update the lightning settings in the software and it immediately updates on the mouse. The only thing that isn't working is the keybinds.
I have tried both firmware versions, USB 2.0 and 3.0, multiple reboots, uninstalling and reinstalling the CUE software, etc. Nothing has helped.
My system specs are updated on my profile..
Any ideas?
