How can I get my Sony 3 CD Changer micro hifi component system CMT-EP707 t?

I disassembled the system and stored it during interior renovations. Now that we're back in I have reconnected it and found that "Protect Tray/Disc" message is all I get when I put it in the CD mode. I've removed the three CD's that were in it and I still get the message. When I disconnected the speakers with the CD changer powered I could open each tray and remove the CD's and protect them. When I then, with the changer still powered, tried to reopen the trays, I got the protect message again. I did push the large spring loaded dome button on the bottom of the changer's chasis. When removing the changer from its storage packing I did hold it upside down for a second or two and did hear some stuff moving around in the changer. Could this bear on my current difficulty?