Q: Express suddenly stopped extending network?

My Airport Express was extending my network to the basement (and using airplay to a stereo) from my Airport Extreme network. Lately it stopped working. Although the AP utility says it was connected and had excellent signal, the "info" button said it was unable to extend the network check all the settings blah blah.I did of course however no settings actually changed. I did a reset, moved into the same room as the main airport and it will see the express, collect information, and try to join then says an error occurred please try again? Any advice is most appreciated.