Before anything else, there are two things worth trying — and out here, saving a call-out is worth a few minutes.
Start here
If it hums but will not turn, the motor is fine and something is jammed. Switch off the power at the wall, use the small hex key that came with the unit to free the flywheel underneath, then press the reset button on the bottom. If it is silent, the reset alone often does it.
On septic, think twice about using it much
This is the important one for Awendaw. A disposal sends a great deal of extra solid material into a septic tank, filling it faster and making the drain field work harder. Some systems cope; many would much rather you scraped plates into the bin. If you are on a tank, that is worth knowing before you rely on it daily.
When it really is finished
Water coming from the body of the unit rather than the connections means it has rusted through and cannot be repaired.
What it does not handle
Cooking oil and fat, which set further along the line and are particularly unwelcome in a septic system.