The amp inside the motor compartment either has a reset button or may need to be turned off/on to be reset.
Also, sometimes you need to initiate the transducers by using the inside auxillary pad on the hot tub. Try turning the volume up on that pad first.
I tried to turn up the volume on the pad but it is not working and I cannot find a amp inside the motor compartment. I may have to call a tech out to fix it. I do not see any access to any other compartments so I cannot imagine where the amp may be.