Transmission any gear only revs the engine?

Hey all. I drive V6 vehicle listed above. I recently, and quite literally, rolled into the driveway last week. It was lucky, I turned around at the corner to get something from the house before running errands. Just as tires touch driveway, I lose any acceleration I had.

Pressing the gas in any gear only revs the engine. I've checked the oil, it's gtg. The transmission fluid was dark (I've had the car for 2 ½ years and hadn't messed with it until now, I'm unsure of the previous owner, and after a drain and pouring new fluid in, I'm still at square one. I tried to drain and refill again a few times, all on a flat surface, being careful to fill only to the cold line. Letting the car get to normal running temp, I check the dipstick again for the hot line. Seems normal. I've shifted through all the gears, and let it sit in one gear before shifting again. The engine only revs.

I'm no gear head, I'm learning as I go. If this is some sort of electrical or part issue, I'm lost as to what to look for.