I am replacing a wall light fixture in an apartment that, according to the tenant has never worked. The fixture has a black wire and a white wire. The switch is in a plastic box and has red, white and black wires connected and a bare copper wire that was not connected to anything. I tested the fixture as wired and got no power. When I introduced the bare wire into the equation, I got power at the switch but not the fixture. I suspect the box has been incorrectly wired but I haven't done a lot of this work and am confused as to what wires go where. Any help would be appreciated. Thanks
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