Last week after uninstalled Visual Studio 2017 and installed 2019 my cover stopped working.
Tryed everything: deleting drivers, force drivers update, fresh windows install, restart, shutdown, clean contacts... Even try the recovery image rendering my surface useless and and to install Windows from a image.
So after all this the cover has a erratic functioning: some short spaces work, most of the time is not detected, and sometimes keeps shifting from detected/not detected by windows keeping asking about entering tablet mode.
The cover doesn't light up in uefi menu so I think it has any problem, buts a strange coincidence after installing/install visual studio.
Even more strange so much people complaining about this problems with covers. My device has 5 years, buts completely functional (i5/4gb/128gbssd) not used a lot.
After half a day I've been convincing myself to buy a new cover. So went to a store, and before buy a sp4 cover I asked to use my sp3 in the demo cover. Found the same issue: cover not detected, sometimes is deteted, but it has a erratic connect/disconnect behavior. After all this I must conclude that it's a surface problem. I have all the updates so, guess it's not a firmware issue. Probably hardware malfunction now, but it's a strange time window for this to happen