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Unfortunately, if the treadmill tripped a breaker (as opposed to your having switched it Off by the breaker), then something considerable may be wrong with it.
What were you doing at the time? running, or just walking? or not driving the belt at all?
If it doesn't trip a breaker now, good... but, have you recently adjusted the belt tension?
If the belt is adjusted (or, has shrunk up with age, and lack of lubricant...) too tightly, then it can stop the treadmill from working or running. An over-tight treadmill belt can cause wear, or even damage, in many other ways, such as by overheating the motor.
The solution that you should try first, is that the belt might need readjusting and lubrication (with the special, non-grease, lubricant these treadmill belts generally require.)
The belt should be adjusted, generally speaking, so that it is loose enough that it does not quite slip, but nearly that loose.