Transmission fluid will not drain?

My car was having trouble shifting (hesitating when driving). I decided to do a full drop-pan fluid and filter change on the transmission fluid after looking at it and seeing it was black and super low.

Dropped the pan and old filter, old fluid drained well as expected, put on new filter, gasket and pan. Tried to drive - transmission doesn't work at all now. Does not engage. Car starts and revs fine with gas pedal but won't go anywhere in drive or reverse.

Took the pan and filter off again to see if maybe I didn't install the filter quite right. The new filter is bone dry meaning it hasn't been getting any fluid at all. The transmission fluid now won't drain at all. Despite the pan and filter being completely off the vehicle the transmission fluid tank is full. I have no clue why it won't drain. It's all fresh fluid so it's obviously not gelled or anything.

Any info is appreciated!