hi,
i have similar issue with type cover....My type cover perfectly working with other sp4 but not with mine.. after i uninstall the drivers manually, it detect and reinstall every time.. note that the fingerprint ID is working perfect even though the keys and touchpad not working.....very strange..i did all troubleshooting, installed fresh windows 10 and it's same...I've tried other type covers with my surface pro 4 and it is the same issue.
Additionally to say some times the type cover come back and work perfectly after a couple of days keeping the system shutdown in my bag, but goes off if i restart or shutdown or went to sleep...this has been continuing since a month...
the only remaining thing is to take it to a Microsoft store..but i don't have one in Riyadh, Saudi Arabia.. please let me know what to do..