This is probably a dumb question, but have you tried removing your phone from the case and re-inserting it? I had the same case (just exchanged it for something else because I got tired of flipping the darn thing around) and there were a couple of times when it stopped working, and after removing the phone and putting it back in it worked fine again.
Also, just a heads up. I did get some small, but kind of deep scratches on my screen and there were scratches on the plastic part of the case in the exact same area, so something got in between and scratched my phone. I was always afraid of that, and the first time it happened, I knew I had to find something else.