AirPort Extreme with Express for AirPlay

I've had a WiFi network configured for music streaming for many years using an AirPort Extreme base station bridged to an AirPort Express (connected to my audio/stereo system) running a Mac G5/OS 10.5.8.

I recently had to rearrange computer components which required everything to be powered down; After rebooting, I decided to revise password and security settings which resulted in the AirPort Utility app not being able to locate the AirPort Extreme. I reset the base station to factory/default settings and recreated the network; AirPort Utility now identifies the base station but the AirPort Express does not appear in the scan list.

Any suggestions for this old-school setup would be helpful.