Nothing is wrong with your impeller. I have an Aquatop cf500uv (which is the same filter as your Sun canister filter) and I have the same problem. Everytime I unplug the filter or there's an power outage it never wants starts again. All i here is a clacking sound from the motor. It takes at least 20-30min to get my filter going again.
Please checkout my thread titled: "urgent help needed w/aquatop cf500uv canister filter"
You should be able to get it started after reading that.