If you have this issue, please close Fnatic OP from the Task Manager and start it as administrator. If that does not resolve the issue, can you please uninstall the OP software and re-install it again from our website: https://fnatic.com/gear/en/op/.
Then restart your PC.
If you are still experiencing issues, please reset your device. You can find more info here on how to reset your Generation 2 mice/keyboard:
http://help.fnatic.com/support/solutions/articles/77000304277-how-do-i-reset-my-clutch-2-flick-2-mouse-
http://help.fnatic.com/support/solutions/articles/77000302978-how-do-i-reset-my-ministreak-streak-keyboard-