"Also. Co2 tank was recently replaced so I'm pretty positive it's not empty."
A bad connection/leak can easily empty a tank overnight.
It's easy to test to see if it's full or not as described above.
If you have gas, vent the keg and then hook up the gas. Turn the screw and listen. You'll be able to hear gas flowing if its working. If so, the gauge isn't working. If not, the whole regulator isn't working.
If the regulator isn't working, you might want to take it to your local homebrew shop and see if they can help. Even if you could find a professional to look at it, he would probably charge more for his time that it costs to buy a new regulator.