Switching audio output from menu bar to AirPlay no longer works

[hewhore]

I have two second gen. Airport Express configured to join my (non Apple) wireless network. Their only use is as AirPlay audio outputs. The units themselves function fine, (confirmed by playing audio from my iPhone), but I am now unable to switch audio output to either of the boxes from, for example, my bluetooth headphones by clicking on the menu bar speaker/sound icon and then selecting either of the Airports. Selecting either of the outputs from 'Output' under 'Sound' in System Preferences DOES work.

 

[goodfidelity]

Did you find a solution for this problem?