I have seen this in the Past . It is a one of 3 items based on your wiring.
1. Bad Breaker. The tripped breaker spring is faulty and the switch does not trip.
2. Bad Outlet - Depending on the wiring from the panel to the pump, check for a bad Outlet or if there is a GFI, bad GFI.
If a bad GFI find the cause of the Ground fault .
I woud repalce the Breaker first , a small low cost reapir.