2003 Ford Windstar won't engage in any gear except park

I have a 2003 Ford Windstar, I drove it on Friday night came home and parked it , went out the next morning and the gears would not engage.The car runs, the back up lights come on, we replaced the transmission range sensor, what else could be causing this?

A lack of transmission fluid? This would be the most important thing to talk about if you’re looking for remote guesses.

Transmission fluid is full

Since there is enough fluid and it appears that the manual valve is operating, now you have to see if there is line pressure. Connect a transmission oil pressure gauge to the line pressure tap and see what the pressure is reading in Drive and Reverse. Get back to us with the pressures and we can go from there.