Car CD player installation question, why is there no power?

So I am sure some people will say you shouldn’t mess with things you are not qualified for..and I agree…

I have installed CD players in all my cars with no problem so my friend asked me to install his. Everything went great except the wire harness(the part where you twist the metal wire things together sparked while we tested it. It worked until that spark and now the interior light and the cd player have no power. We replaced all the fuses on the car even though non of them seemed broken. Any ideas? None of the wires seem burnt and the spark was very minimal. I have no idea though… :(