Last cell in brig won't open?

I have bought all characters from the cells, activated every puzzle and the red light thing above cell 4 does not glow when I have a sith character so I can only get 3/4 lit up in blue. Don't try telling me I did something wrong, because before I opened all the cells the sith panel worked and I activated it but nothing happened and now I can't use sith force on it anymore. Restarting does nothing it is saved permanently this way.