There are a number of bushings; that are in the shifter system, that can fail... causing shifting problems. DieselGeek, makes many of these bushings and they really do help. Take a look at the bushings and the videos; that DG has posted, to see if they apply to your situation.
Dieselgeek Shifter Parts
I would check with the shifting cable ends and the shift gate on top of the transmission, see if anything is worn out (cable end bushings) and see if you can get the car into reverse by hand there.
The first thought; would be that something has broken or come undone. You can also; try adjusting the shifter linkage and see if that helps.
https://www.youtube.com/watch?v=sheTKD03hmo
Dieselgeek Shifter Parts
I would check with the shifting cable ends and the shift gate on top of the transmission, see if anything is worn out (cable end bushings) and see if you can get the car into reverse by hand there.
The first thought; would be that something has broken or come undone. You can also; try adjusting the shifter linkage and see if that helps.
https://www.youtube.com/watch?v=sheTKD03hmo