Car has no power

So I accidentally left my interior light on over night, and the battery was drained. So I took the ol’ zap box out and put it on charge for around 6 hours until it was reading 12v. After I put the battery back in I assumed I would just be able to start her up and it would be back to normal. Key word there is assumed. There is absolutely no power to anything, no interior lights, no horn, no break lights, nothing. Ive checked all the fuses including the 80 amp main fuse, nothing wrong there. I got the multimeter out and checked if there was power even getting to the fuses, and sure enough there was, and both ground connections where fine. I’ve sanded down the terminals and applied contact cleaner, still nothing. Im honestly lost as to where the problem lies, because as I’ve said all circuits in the car seem to be getting 12v. If anyone could help that would be great!