Gentlemen I have just encountered this error myself and when I tried using the above method to revert to the original functions it failed. No matter how many times I tried forcing the button assignments they refused to work correctly....that is until I made the changes in software in conjunction with unplugging my mouse and allowing it to completely drain power. Once I plugged it back in the buttons worked correctly so IDK what else to say.
To be honest this is my first and last corsair mouse as the software is clunky and not very user friendly like Logitech's. Plus the scroll wheel outer rubber tire like covering came loose and was just spinning around the metal inner wheel until I super glued it down. I've never had a Logitech mouse, or any other mouse if I'm honest, do this to me before. I've learned my lesson the expensive way!