I have a 1997 Honda CRV. I just replaced the thermostat like 5 days ago. Radiators been flushed as well?

All the fluids are fresh and at the proper levels. There are no visible leaks of any kind of fluids but the car still overheats usually once its been driven for about 15-20 minutes. I take the radiator cap off and the coolant is not moving through the radiator. Would this be a water pump failure or could it be something else?

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