I can turn everything on but the belt does not move. I used it one morning and then that evening it would work

The single most cause of no motor output is failure of the DC motor control. Before you attempt to determine if it is the control, you must first rule out simple things.
1) Make sure you have power in the wall outlet by plugging in a lamp, etc. into the same outlet the treadmill is plugged into to test. Plug it in the exact same receptacle. Sometimes in an outlet one receptacle will work and the other won't.
2) Make sure any breakers are fuses that may have tripped or blown have been reset or replaced. Your local Radio Shack can help you test the fuses. Use the same type of fuse. Changing the value of the fuse can be dangerous or cause a fire.
3) Make sure the power switch is turned on and the safety key is inserted into the console if you have a safety key.
4) Look for any test lights on the power boards beneath the motor hood. Use caution when removing the motor hood because you may still have electricity in the motor area even if the treadmill is unplugged.
5) Test for a motor control failure. Typically if you have a failure, the treadmill will continue to turn on and operate normally until you try to input speed. If the treadmill operates on what we call a closed-loop system, it will give you some type of error message. If it operates on an open-loop system, the computer will run normally but the motor will not turn.
6) If you have a multimeter, you can test to make sure you have DC output from the controller spades. First make sure you have 120 VAC going in to the controller. On most controls, you can use a linear taper potentiometer or jump the W and H circuits of the control with an insulated wire or insulated pliers and apply AC voltage. The DC output spades should output DC voltage if the control is good.
7)
Cordless drill battery- get a fully-charged, 18 volt (preferred) cordless drill battery and on most treadmills connect the red and black motor leads to the battery (some have different colors but if you have two wires and get it hooked up backwards, the motor will just run backwards and won’t be harmed). If good, the motor should operate at about 1 MPH