I had gone through many threads on here to fix the issue of the mouse not working when wired and a lot of them were about uninstalling Synapse and it was back up - now if you’re like me and use a wireless Razer headset too, it prevented this from working if you removed Synapse and also makes a lot of features redundant so I needed something else. It was lost in a thread (can’t remember who suggested it), but I tried on the off chance.
SOLUTION:
If you have Riot Vanguard installed, remove it - my mouse IMMEDIATELY worked again when this was uninstalled and didn’t require tampering with drivers or software directly associated with the mouse.