The pickup cover is normally connected to the ground connection on the pickup, to make the cover more effective as a shield. Did you unsolder any connection first? If not, you may have broken the coil connection to the ground wire. Even unsoldering may have left the coil connection loose.

Select the bridge pickup (so the neck pup remains unconnected to the volume and tone pots), then measure the resistance between a pot back and the neck pickup hot connection to the switch. That will give the coil resistance and af its somewhere in the 4k-10kohm region, then the pickup is OK.

If it's open circuit, then the coil has become either become disconnected or a coil wire has been broken in the process of cover removal.

If it's a short circuit, then somehow the coil connections have become linked, possibly with a wisp of loose wire.