airport express "device not found"

Are you using AirPort Utility on a Mac laptop to look at the AirPort Express or AirPort Utility on an iPhone?

We ask because you can use the Mac to check the quality of signal arriving at the Express. (The "bars" are useless as far as determining actual signal quality.)

If the WiFi signal-to-noise numbers check out OK, the next step would be to roll back the firmware on the Express to 7.6.9 as a test to see if that helps. Neither 7.8 or 7.8.1 have been all that reliable.

If 7.6.9 seems to help, try moving back to 7.8.1 again.

If still no help, you'll need to think about wiring the Express back to the main router using an Ethernet cable connection. I have had zero problems with Expresses that are wired. Always had "iffy" reliability with wireless connections to the Express.

SNR of 25dB could be better. You want to see 30+ if possible to improve chances for a reasonably reliable connection. Even then, there are no guarantees.

Is the Express picking up a 2.4 GHz WiFi signal or 5 GHz signal? If it's 5 GHz, you may have better luck connecting to a 2.4 GHz signal, since it will very likely be stronger......and even possibly faster than a 5 GHz signal.

You probably don't want to hear it again, but in my experience nothing beats an Ethernet connection to the Express for reliability. Zero signal loss and no issues with interference from other WiFi sources. If you can't run the Ethernet cable, consider using a pair of Ethernet over powerline adapters. Not as good as Ethernet, but almost always better than wireless.

7.6.9 firmware was not meant to be a permanent solution for your test, but if things work better on 7.6.9, then you know that 7.8 and 7.8.1 are suspect, as they have been for a number of users.....including me.

2.4 GHz signals are much stronger than 5 GHz signals, so that has a lot to do with connection stability. 5 GHz really only works well when WiFi devices are in the same room or very close proximity to the router.

Signal speed is not really the issue anyway as long as the Express is receiving a WiFi signal of 20-30 Mbps or higher.

For what it's worth.......I actually had better luck with WiFi connections on the Express when it connected using 2.4 GHz, not 5 GHz.

Might be worth a try if you have not already done so.

Good luck!