Is this pump,. one of those flexible impeller pumps?
They can not be run dry-- So-- can you lubricate the flex. impeller with something slippery, and compatible with what you are circulating-- or pumping. (Not drinking water, or a fish tank, right?)

If this is a regular centrifugal pump, is it possible that something is caught between the impeller and the housing, when it is all tightened up?-- can you turn the impeller by hand, thru the inlet opening?
Will the motor start it with the housing removed?

Give us some more clues, and we'll dig deeper.

Mack B