Same issue here, Corsair M65. Some time ago I had this problem and was able to do a repair install, and it worked. Now, repair does not work, even though the attached error indicates that's a fix. Total removal, restart, and reinstall with 3.7.99 release MSI does not fix the issue. Key remap and mouse remap do not work. Text remap works, but only will input in a text field and cannot be used as a game control. Sniper button basically can't do what I want it to do and there doesn't appear to be a fix.
Used the same mouse in Windows 7 64-bit for the better part of a year with no issues. This problem arrived shortly after a new computer with Windows 10 Home.
There is a Windows cumulative update, KB4338819, that seems to be having install problems; I'll see if I can get any traction on that, perhaps getting it to install correctly will have some useful effect. That said, there doesn't appear to be any correlation between this update failing back in early August and my current mouse issues, however.