Where is it leaking? If it's the outside seal, then check the clamps that hold the lid on to make sure one isn't broke. Also check to make sure the 0 ring is seated properly; might also lube it with some vasoline. If it still leaks, replace the 0 ring.
If it's leaking where the power cord comes out of the top, then it's leaking around the 0 rings on the quick disconnect. Check/lube/replace the 0-rings.