...the ability to make changes to the airport is restricted. You can't use the "second generation" airport utility to make changes to the "first generation" airports.
That's what I've run into.
As Apple updates AirPort Utility they drop support for devices,
without any notification of which I'm aware, and all of a sudden your base station becomes unrecognizable, and, in the instance of AirPort Express Base Stations, AirPlay/AirTunes and, I assume, wireless printing stop working...apparently inexplicably.
This Apple doc details which AirPort devices are compatible with which versions of AirPort Utility, and I assume that my 1st Generation AirPort Express (802.11n) Base Station will no longer be on the list if Apple ever gets around to updating it for Yosemite.
Googling around, I found
AirPort Utility 5.6.1 on OS X 10.10 Yosemite (more
here ), but I haven't gotten it to work yet.