I'm curious... did it just stop working suddenly, or did it stop working gradually? And did you make ANY changes to the bridge, guitars wiring, etc? One thing a piezo requires is pressure on the bridge saddle to function. Recently, after I changed the bridge saddle in a Martin which has an under saddle piezo, the 6th string stopped working thru an amp, but the other 5 strings were fine. It turned out to be that the saddle wasn't seated properly. Its a full length under saddle piezo, so that's a different set up compared to individual saddles, such as you're dealing with, but the concept of string pressure on the piezo is the same... the 6th string was not putting any of its downward pressure on the piezo because the saddle wasn't completely seated, due to the saddle fitting a little too firmly in the bridge slot. That was a much easier fix (potentially) than what you're dealing with.
Your Hollowbodies issue could be something as simple as a wire that came disconnected, or it could be a number of other issues making the repair more difficult to diagnose. This is gonna depend on whether or not you're familiar with, or comfortable with working on a guitars wiring, which gets kinda complicated where a piezo combined with magnetic p/u's are concerned. If you're not comfortable working on the guitars wiring, are there any guitar shops nearby with a competent repair tech? (We can leave Guitar Center out of that conversation. They don't typically have anything resembling a competent "tech". They have "restringers" and MAYBE someone that can do a set up, but I wouldn't trust them with diagnosing that issue, unless you really know their "tech" to be competent at diagnosing an issue like that).
If you're really up against a wall with this, my suggestion would be to call PRS and ask about the isssue, and possibly having them repair it. They would certainly know more about that guitar than just about anyone aside from a truly competent tech.
