light fixture with no power
A wire can break at the nut and become disconnected - you have 4 wires - so I am wondering the wire nut size if it is too small. 

Did the fixture have stranded wires or was it solid ? 

I am guessing your wires are not connected anymore whether a wire broke or one slipped down to the insulation of another.

You stated you have 4 whites and 4 blacks - wire nuts for fixtures typically will support 3 wires of proper gauge and it is a stretch to get 4 wires into them - with out up-sizing the wire nut.

Disconnect the wire nuts, intertwine the wires and reinstall the wire nuts..

Don't over think this - it worked once already (did the lights all burn out at once - probably not. When you pushed the wires into the box (8 wires cramped up there ), then it did not work. - Your wire nuts probably need an up-size.