Only the Shiatsu, Pulsating, and Soft stream are rotating jets. The deep tissue jet is not designed to rotate.
Remove the face plate and make sure you can spin it from the back side. It may be worn out or have debris in it.  Clean if necessary with a hose and pressure nozzle.
Turn on the therapy jet pump with the face plate out and make sure the therapy nozzle is working good and has not been blocked by debris. If it is blocked use a socket and long extension to remove the jet and blow out the line and clean the jet opening.
If after cleaning the jet and clearing the line it still doesn’t spin replace