Had water leaking out of my ceiling and down a kitchen light. Happened while running the washing machine. Discovered the a/c pan was overfilling and going over the top of the pan and down into the kitchen. For some reason the washing machine is draining into the a/c drip pan. Washing machine is on the 1rst floor and a/c is in the attic. Any ideas?

Unless the washer drain hose is totally fixed to the drain, I can't see how water could flow, or be pushed, up one story. I would expect it to flow out the washer drain connection. Water is pretty heavy and to push it UP into the attic would be a challenge. How is the washer drain hose connected to the drain box?
Not sure where you live but, in Georgia, drip pan drains are directly piped outside and in front of a window so you can see the water coming out.

Both should have separate drains and be independent of each other and highly possible both have a blockage. Unusual for one to affect another, but possible if they were for some reason connected somewhere. Never seen that. Trace the lines and get back with us if you can.