Are you saying the shift lever does not physically go down into Drive? Or does the shift lever go into drive but the vehicle won't move?
If the shifter physically won't go into drive have your husband look at the whole shift assembly from the steering wheel down to the transmission. Try to see if something is hitting the linkage and stopping it from moving. He might also spot a linkage joint that is stuck and needs a good spray of penetrating oil to free it up.
The fact that you say it does not move in reverse sounds like the shift linkage possibly slipped and is out of adjustment. Again this can be caused by a stuck joint in the shift linkage causing the linkage to slip rather than move the lever on the transmission.
