I changed the watch cell but indiglo doesn't glo...what should i do?

It is either a screw on case back or a "snap-on. I suspect that it is the latter since you don't mention that you used a tool to unscrew the case back. So getting the back on sometimes is very difficult. I have a special tool for that to apply even pressue and the necessary force and does not put pressure on the crystal. You have to be careful to not damage the crystal. If you don't get it done, then suggest you take it to a shop that has the right tool. If you have very strong thumbs you might get it done.