My iPad cannot connect through airport express, but two phones and another iPad can.

Yesterday, my iPad was working perfectly over my home wifi. Today it is not.

Two iPhones, two Mac Pros and another iPad are working fine.

The connection point is an Airport Express running in bridge mode to an Airport Extreme. The whole setup is a bit rococo but it has been working perfectly for years. We have satellite internet. The satellite modem is in the tractor shed (because it has a flat roof that provides easy access to the dish.)

The Airport Extreme is in the shed - and the iPad is perfectly happy to connect to that. The house (with the airconditioning) is outside the range of this device. The shed (without air-conditioning) is about 40ºC during business hours, so I am not keen to spend too much time there.

A pair of Netgear access points with outdoor antennae relay the signal to the house where it goes through a switch to the Airport Express, which is configured in bridge mode.

Airport Utility on the iPad reports that the Airport Express is Green and shows a direct connection to the internet which is orange. It can open and edit the Airport Express settings.

Airport Utility on my Mac shows the Airport Express connecting to the Airport Extreme connecting to the internet and all statuses are green.

I have tried the following remedial actions:

• iPad: Forget this network then re-initalize the wifi connection
• iPad: reboot
• iPad: reboot with extreme prejudice (click Vol-up then Vol-down-then shut down.)
• iPad: renew lease
• iPad: Change the iPad's DHCP handle
  • At this point, I notice that it's address is 169.254.36.192, which the address it uses when it cannot get an address.
• iPad: Manually assign an appropriate address of 144, outside the DHCP range of 2-100.
• Airport Express: Restart
• Airport Express: Activate guest network.

None of these actions fixed the problem or changed the symptoms.

The iPad is running iOS 12.1.1. I have no idea when it updated, and I cannot find anything on the interwebs that tells me how to find out. The other devices are all on 12.1 or less.

Any thoughts?

Versions:

• The bad iPad: 2017 12.9 (aka the last truly flat iPad) Model MPA42XA running 12.1.1
• Airport Express: 2nd Generation with version 7.8, no outstanding software updates
• Airport Extreme - 4th Generation (i.e. a flat one) with version 7.6.9, no outstanding software updates
• A good iPhone: 10s running 12.1 - connects perfectly, no errors.

Remember - all this was working perfectly yesterday. The router-relay-bridge configuration has been in place for about 8 years. It all works fine for five out if six devices, and the sixth device works when it is talking to the Airport Extreme.

I think the Airports are not the culprits. It has to be the iPad - but why does it work with the Airport Extreme and not the Airport Express? It could be a hardware problem, I suppose - some transistor in it's WiFi modem died overnight so one vital band stopped working that is not required to talk to the Extreme, but it seems unlikely...

Any thoughts? Anything I have not tried, other than completely reinitialising the iPad, which iI cannot do because I don't have a way to back it up (Must get one of those Thunderbolt and Lightning, priced very, very fright'ning cables. Sorry Freddy...)

Thank you, as always, for your help.

Russ

PS - Why does this forum ask for device "generation" when the device itself cannot tell you that? And why does Jony insist on putting the Model number on the back in tiny dark gray on silver print that I bet even he cannot read? And why is the model number displayed in Settings - General - About (MPA42X/A) not the model number that is (allegedly) illegibly inscribed on the case (A1671)?

Having three different descriptions for the same device with only two of them available on the device itself, and then asking for the third one to allow a post on this discussion forum indicates ... something. I'm not sure what it is, but I wish they would make it easier one way or another. The Airports tell us the generation number (although reluctantly - we have to Option-Double-Click the device in Airport Utility to get this extra information - why hide it?)