I lowered the ceiling fan light fixture to tighten fan blade. Then reinstalled the fixture and now the fan will not work although the light does.

First of all, you don't need to lower the fixture to tighten the blade screws. A short screw driver or ratchet head would have saved you the trouble you are in now. Chances are that while you were tightening the screw the fan motor was pulling on the wires. Just recheck the connections maybe even remove the twist caps and test voltage with a meter. I'm sure you will find an open circuit.

Sometimes you do have to remove the light to tighten the blades.

As Ballenger says, check all connections. Check to make sure the blades can still turn freely by hand. And check to be sure the reverse switch is firmly in the up or down position.

General ceiling fan troubleshooting and help FAQ- Ceiling Fans N More