First thing to try is check how tight the 4 bolts are the hold the AC units down to the roof. They should be about 5 ft-inches tight. This will snug the AC unit down to the roof and if that's the problem the leak should stop.
Next, look up into the AC filter location. Remove the filter and look on either side, there should be clear plastic hoses attached to a Tee. The AC units have drip pans mounted underneath on either side of the AC. The condensation drains into the drip pans and through the plastic tubing to the ground. If installed right, even if these plug the condensation should drain to the outside.
Pull the hoses off the plastic Tee and use compressed air to blow out the hoses.
I had been having a problem with my rear AC unit occasionally leaking, tighten the 4 bolts solved the problem for a little while. Then the front started to leak so I decide to replace the roof gaskets. In both cases the gaskets were not lined up correctly and in heavy downpours there was a chance water could come over the top of the first gasket. I installed 2 new gaskets and drip pans on both units. The drip pans were still usable but very brittle so I went ahead and put new on.
Here's a post I did on it showing the problem.
https://www.irv2.com/forums/f115/rep...ts-510277.html