CD changer not working on '95 3 series and '99 M3, ideas?

I have a '95 3 series and '99 M3. Both have a 6 disc CD changer in their trunks. Both have recently stopped working. The message "No Disc" appears when you try to play a disc from the changers. Is there a common problem with this series' wiring or typical issue that I can try and troubleshoot and fix?