Sounds like he didn't wire it back up properly. If the pump hums and doesn't turn I would suggest one of two things:
1) He didn't wire it back up for 240V and it's only getting 120V. Test it with a meter for correct voltage.
2) Unlikely, but the bearings in the pump may have seized. Rotate the pump by hand to see if this is the case.
I'll go with door #1.