Pump doesn't move water

I moved into a house that has a utility sink in the basement. A pump is installed beneath the sink to pump the water to the waste line. Anyway, the pump has a manual switch to activate. When I flip the switch the pump makes a low hum, but doesn't move any water. It's a "Shellback" brand pump and says it has only one moving part. Can anyone suggest why this is not working and if it may be an easy item to repair? Thanks.

I was wondering if when you turn the pump on, does it kick itself back off? If it does, there's a problem with the pump motor. The internal overloads would shut the motor off.
If it doesn't turn itself off, then there is probably something blocking the inlet to the impeller and will need to be cleaned. I'm assuming the pump is inside a sealed sump. Open it up and the pump should be fairly easy to remove. While you have it out, look at the pipe right above the pump discharge and below the checkvalve. The could be a small hole in the pipe. Make sure it isn't plugged up. The hole is there to prevent the pump from getting airlocked. (That itself could be the problem,too).
Ron

pump

The "one moving part" is not moving because the pump is jammed. Either because of disuse, or somthing caught in it.

Thanks for the replies.

The pump does not kick itself off, it continues to hum. It hasn't been used in about 6 months, so maybe it is blocked or stuck due to disuse. The pump has 2 sections, one is the main body that contains the copper coils, the other is off to the side and looks like 2 semi-flat disks with a rubber gasket in between. There is a small rubber tube running from the flat disks to the top of the "main" section connected to a small brass feeder tube.

Any idea on how I would unblock/unsitck it? I can't figure out how to get access to the inner pump mechanism.
Thanks!