I had this problem after a Win 10 update. The mouse stopped working both USB and Bluetooth. I tested a different mouse and that didn't work either. Touchpad worked fine. So I called Dell tech support and they suggested I uninstall Windows update and re-install the chipset drivers that they provided. I did both and mouse still didn't work. Then tech support suggested I do a Windows Restore. Again that did not solve the problem. Then they suggested I do a Windows reinstall. At this point I got annoyed since I have 30 programs that I use for my business and a total Win re-install is out of to question. I thought there must be another simpler way to solve this problem. So I did an online search and found a fix. It was a very simple problem and needed a very simple fix:
I was able to fix this problem by adding a missing MultiString value to this registry key:
Value Type: Multi String
Value Name: UpperFilters
An article that explains it in a very round-about way is here:
The Multi String Value Name: UpperFilters was missing so I added it and the mouse started working and everything is good to go!
I was very disappointed with the Dell support team I contacted. They gave me the run around for 3 days for such a simple problem.