M&S Systems MCD-6 6 Disc CD Changer display of "err... (by 2 users)

I receive a "err 01" message in the display when the MCD-6 CD Changer is turned on. Also when eject button is pressed the cartridge does not eject, although a motor sound is heard for approx. 2 sec., during which time a "0.00" is displayed. If while trying to eject, another button is pressed, (Track, Search, etc.,) a "no disc" message is displayed (even though discs are loaded) and returns to "err 01" when the moter sound ceases. Prior to all this, the unit operated properly.