in Airport Utility my airport express says "device not found"
in Airport Utility my airport express says "device not found" I do not want to tell it to forget it. What should I do?
Not sure why you marked your issue as "solved", but what is done is done.
At this point, you will need to perform a Factory Default Reset or Hard Reset on the Express and then try to set it up again.
How to reset your AirPort base station - Apple Supportsupport.apple.com › en-us
If you are still having issues after this, we'll need to know what version of the AirPort Express that you have, what you want it to do on your network, and whether you will be using a Mac, or an iPhone / iPad to set up the Express.