If you got from overseas, you may have to change for our zone, even you can change the setting to accept all zones.
While a decent guess, I'll agree with Sa-Dono that the region code probably isn't what's going on here.
As Sa-Dono mentioned, the region code issue wouldn't effect CD playback.
Yes, it is technically a region 3 player. But it's sold w/out region coding in HK. Which was one of the main reasons I bought it over buying a DV-47Ai locally as I have many region 2, 3, & 4 discs. It was tested with region 1 discs before it was shipped, and it played them fine. Though I don't know if it played a region 1 RCE disc or not.
And when I was trying to get it to play anything, I did try discs from regions 0, 1, 2, 3, & 4 (I don't have any discs from regions 5, 6, 7, & 8, so I didn't try any of those). Not to mention single & dual layer discs from a few different regions. Everytime it just spit them out like there was no readable disc in the tray. It didn't spit them out and say "wrong region number" or whatever it is that my DV-333 says when I forget to change the region on it properly.
I'm afraid there's something mechanically or electrically wrong with it. And was hoping that's it's just a quick fix that I didn't notice in the service manual I've got for a DV-47Ai. I can't run diagnostics as I don't have a service remote for it. And Pioneer won't let me buy one.