Unfortunately, we cannot see your network or read your mind....so we must ask for your help.
How are you trying to configure the Express?
What service will it perform on your network?
What does the AirPort Express connect to? Wirelessly? Wired?
With some basic information, we can get started on your issue.
thank you Bob,
configuring after a hard reset, with airport untility 6.3.2. my osx 10.9.1
airplay from macbook pro, iphone 4s, ipad mini
connected via 3.5mm stereo jack to hifi, other than power nothing else connected
so i go thorugh all the steps, "join a network", it will work straight off, but if I stop, and try to start again...nothing. Then when i run utility, I see it with a yellow triangle, and when i highlight, mesage is "device not found". Never had this issue with previous airport express (1)
Sorry, I am not familiar with that product.
The steps in this Apple Support document have helped some Mavericks users with the "disappearing AirPort" issue:
Worth a try: