Harman Kardon FL8350 5-Disc CD Changer "region error" Questions

...error,so what may be the cause I have started receiving this display. No disc. - Load a disc into the tray. Disc has been loaded upside down. Place the disc with the label side up. Disc region code ...

...Region 2. An error code shows 'Incorrect Disc C104. Of course the manual states this means the disc is incompatible. However as gives this message to the vast majority of discs it has played before, ...