Devices can't find the Airport Express after...

You might check your SysPrefs > Network to see if switching to the Network name associated with the AP Express will allow you to use it.

I have a similar problem in that I have an AP Extreme dual band that my iMac is connected to via ethernet. It is also set up as for my wireless network for other Apple devices. I had been able to stream iTunes music to the AP Express b/g wirelessly and it was connected to play music through my stereo. I can no longer do that, I guessing due to changes that happened w/ an update to iTunes and or OSX associated with AirPlay functionality. If I go to SysPrefs > Network and change from "Automatic" which is how the AP Extreme is set up to my "Living Room" > WiFi device I can stream music to the AP Express but the iMac is no longer connected to the AP Extreme or the internet. This set up has worked for years and now no longer does without changing settings that I'd rather leave alone. The other thing that is also happening now is that the AirPort Utility indicates that it is no longer compatible with the AirPort Express base station. I'm guessing if I want to buy a new AP Express, which I don't, I could probably solve this issue. I talked w/ one of the Genius folks at the local Apple store and he hadn't heard of anyone else reporting this issue as of yet.

Since i updated to El Capitan and iOS9 all my time capsules and airport express devices and their respective networks are not visible to ipad. Except the main base station.

Manually adding network name and password sometimes wirks, but then sometimes it doesnt find the network. One of the stations is completely invisible to all Macs, Macbooks and iOS devices completely except one iMac which can see it.

Reinstalling, or restarting iPad, Mac, Airports, and resets do nothing

Its Apple. They have screwed up with their new updates. Many older devices dont work as they used to. The iOS9 Update has turned out to have messed up many things, as has El Capitan

I might as well have one single airport as the other two are now useless. Im sure the other one will stop working after apple updates again too. Since the last update my Tpmb Raider Underworld game is disappeared from US Appstore too, as has OSX server, and a host of Movies i Purchased. All missing from purchase list, or wont download because they dont exist in the US store anymore. SAo if you bought it.. tough luck you got robbed

Same goes for airport extreme and time capsule.. if its 2012 era.. get ready for apple to 'make it stop working'

I tink they want us to buy new stuff, and so deliberately cause the old stuff to deprecate

wwhat do you mean can't find airport express? Do the airport utility on Mac and iPad see both devices when express is not on Ethernet? If yes, then that is normal.

you will not see separate wifi Ssids for the 2 devices, example if u have SSID jingle network on extreme and express is wirelessly extending it, you will only see jingos network to select from on all your devices.

if you want to test that your setup is working properly, get wifi analyser app on android and check the direct wifi signals available along with MAC addresses, u should have 4 different Mac ids for same SSID jingos network for 2.4ghz and 5ghz multiplied by 2 for both devices.

the android app wifi analyzer can be useful to see signal strengths at different locations in your house. Use that to position your devices Best.

also, assign a 5ghz network name as something else for your extreme and extend that network, might provide better connectivity Around your house. in your express settings, u can also assign a third different name for ITS 5ghz network.

for eg. Extreme has ABC and ABC5 for 2.4ghz and 5ghz respectively. Set express to extend ABC5 and name its 5ghz as abc55.

you will end up with 3 Ssids, abc (only extreme 2.4ghz), abc5( extreme 5ghz and express 2.4ghz) and abc55(express5ghz). This allows you to have more flexibility to choose your network in your house rather than have the device choose one for you.

hope this helps.