Same problem, remove cover may have at least 2 drain holes; one on each side, clogged.
Solved my problem.
When you remove the cover take a picture of the serial number, model number plate. Or, write down the info. You can search the manufacturer.
Caution when tightening the AC from the inside, don't over tighten as it could damage the seal. There may be tabs along the rim where the ac meets the roof that provides a guide on how tight the ac should be. The installation instructions may provide in on how to appropriately tighten the ac.
