IOS/iPadOS 13.5.1 New Bug

Well, I have tracked down the issue. It's a bit complicated, but now resolved.

It's something with my router (a DLink) that only showed up with the 13.5.1 update.

Why I didn't figure this out when I tested it on just my cable-modem, was that the iPhones seem to be caching and sharing network information. When the iPad was on the dLink, then I eliminated the DLink, and tested my cable-modem, I was then alone on it. To test putting all my devices back, I renamed the cable-modem's wifi to be the same as the DLink's.

The issue cropped up again after a few minutes. It seems the "bug" with IOS 13.5.1 and the DLink makes some cached setting in the iPad, that carries the bug to the cable-modem. Resetting (forgetting the Wifi SSID) had fixed it (so all was good for a few minutes) until more devices came online. They seem to "share" information about their stored SSID settings, including whatever this cached bug was.

Same issue when replacing the DLink with the Apple Extreme router.

Deleting the Wifi SSID off all Apple devices and reconnecting each one resolved the issue on the cable-modem.

Putting the DLink back brought the issue back, proving it was the DLink that had the 13.5.1 incompatibility - and was somehow "infecting" the 13.5.1 devices with some setting.

Removing the DLink, putting in place the Apple router, deleting all the SSIDs from the Apple devices has now removed the issue.

So in summary, the DLink router, which was fine until 13.5.1 is doing something to mess with 13.5.1 devices that they remember, and carry to any other router with the same SSID. Apple has changed something - I'm not qualified to say if it's wrong, but it certainly caused this issue with a DLink router that was fine until the update.

The DLink is no longer part of my network. Perhaps Apple will still resolve this (or DLink will, as it's fairly new and v.1.0 of its firmware is still the latest), but until then, I will live with my old 802.11n, and give up my ultra high-speeds.

This has been an exercise and a half, but it is solved, and may help someone. You may not see the prompt about cellular if you're not downloading something large from the App Store, but you could still hit the issue where it won't download a major IOS update, and doesn't say why, or maybe your Photo Stream isn't working. I do see a lot of people on the IOS 13.6 and 14.0 beta forums complaining that they are stuck while trying to update. I'll ask some of them if they happen to have a DLink router.

Oh, trust me, I have done everything, including restoring IOS devices.

Today I had it down to just the cable modem with Wifi and one iPad (worked as expected). Had DHCP turned off, and hard-coded the iPad. Worked fine. Turned DHCP back on, set iPad back to DHCP, worked fine. Added a couple of devices and all was well. Had 5 iPads on and two iPhones and at first everything was fine - then after a few minutes the first iPad started showing the same issue again. Gave up and enabled all 27 or so wifi devices and opened a beer instead.

I then put the upstream router back, and moved devices to it. Tried one device with the cable modem wifi again, and all is OK.

Also tried sharing my hard-wired Macbook's network (hard wired to same cable modem), and with a couple of iDevices attached, they work fine.

There could be one device somehow interfering, but only interfering with iOS 13.5.1 devices and tricking them into thinking they are on cellular! All settings have been reviewed and all are correct so far.

Attached screenshot is on my Wifi-only iPad. I'm stumped. It's got to be something unique to me, but caused by a bug. Apple devices think they're on cell.

UPDATE: It's not my network setup - I removed the router, and went with the cable modem's wifi. Once I had all my devices on its wifi, the problem reappeared. Looking at other forums, others are having different issues, but one seems close - one guy had to turn off his DNS server on his router and hardcode everything on his devices - I don't have that option as I have a lot of devices.

Apple devices running 13.5.1 seem to be interfering somehow with each other. The wifi works, but something is triggering these devices to think that are on cellular. It's almost as if they think they are using a Personal Hotspot, as the behavior is the same.

There's definitely something up with this. I also tried installing the public beta of iPadOS 13.6 on my iPad, but it still has the issue.

It's not that - please see my latest update. It also does it if I take that router down and use my cable modem's wifi without the second router connected. Since the issue wasn't appearing when my iPad is the only device on it, I thought it was my setup, but once I add more and more iOS 13.5.1 devices to the network, it starts the issue again.

It definitely appears to be an iOS 13.5.1 bug. The issue started when I updated my devices. It appears that having several iOS 13.5.1 devices causes the issue. My one iPad with 12.4.7 does not experience the issue, but it is 100% consistent with the 13.5.1 devices. I also haven't ruled out the two Apple TVs. I will pin it down, but the difficulty lies in the fact that adding back devices doesn't trigger it for a while, something gets cached somewhere. I will have to add one device at a time, then reboot things and wait on each.

Also, the second router, it was set up correctly. I can set it up both ways - with one I end up with two networks, the other properly extends it as a single IP network...but both configurations show the same issue. It's not the router. And I have been using this configuration for years and it runs great. It still runs great with iOS 13.5.1, it's just the misleading error about it being on cellular. If I click 'Continue" it works fine.

The only things that fail are Photostream and IOS updates, because they require Wifi, and IOS thinks I'm on cellular.

Yup - there's some issue of some kind - and yes, so far it seems to only affect me!

The only thing that has changed though is the IOS updates - and I should not rule out the Apple TV updates.

I maintain it's a bug that for some as yet undiscovered reason, did not show up until iOS 13.5.1 arrived, and does not affect my IOS 12.4.7 device nor any of my other 23 or so devices.

My and my wife's Photostreams both last updated on June 7th. I updated my IOS devices when 13.5.1 came out. My wife was slower to do her two, but possibly around the 7th. One of my Apple TVs updated itself sometime before then, and the other I had to force it, sometime after then.

I've got more detective work to do. Unfortunately I don't have the capability to analyze traffic. But as I mentioned, I can now replicate the issue with just my cable modem's wifi, with the upstream router unplugged. Only when I allow all my devices on does the problem present itself. Perhaps it is one device sending out some kind of packet over the wifi that confuses the other IOS devices. I'm determined to figure it out... but again it is only iOS 13.5.1 devices that consistently believe they are using cellular and another IOS 12.x does not.

Forgot to mention - my Photostream has also failed on these devices starting about the same time. I suspect because Photostream only updates when it's on Wifi.