iPhone 7 can't connect to Wi-Fi post iOS 15.8.3

Great, glad it worked. Here’s the long answer, if you are interested:

Wi-Fi normally connects to a router, which assigns an IP address using a protocol called DHCP (Dynamic Host Configuration Protocol). But it’s possible to also use Wi-Fi to connect a group of devices to each other rather than to the Internet in what is called an ad-hoc network. Ad-hoc networks use IP addresses in the range that starts with 169.254.0.0. Each device in the ad-hoc network creates its own IP address in this range. When you connect a device to a network it will "ask" the router for an IP address using DHCP. If it doesn’t get an IP address assigned within 30 seconds it assumes that it is an ad-hoc network and assigns itself a random address in the range 169.254.x.y.

There is a common failure mode in many routers where the DHCP “daemon” process in the router fails, and it stops assigning IP addresses, so a new device connecting to the network will self-assign. But any device connected to the router that already has an IP address will continue to work. This makes it look like the problem is the phone or other device, because everything else connected still works, but it’s actually the fact that the router is no longer assigning IP addresses. While it can happen to any device using the router the problem is more common with phones and devices that disconnect when they go out of range, and reconnect when you get “home” and thus get a new IP address assigned. Rebooting the router restarts the DHCP daemon and resolves the problem.

The reason it happens with many different routers is that most routers have the same underlying open source operating system. It’s primarily a problem with routers more than a few years old; newer ones from top tier manufacturers rarely have this problem.

No, but you can troubleshoot the problem. Start by rebooting your router; unplug power for about 15 seconds (many routers no longer have a power switch that turns it off completely).

There’s more to troubleshoot if this doesn’t fix it, but this is the first step.

This worked for me. 4 different iPads would not connect to wifi after 15.8.3 update. Restarting wy router did they trick (so far).

I assume everything you stated is accurate. This one was odd though. The inability to reconnect to my wifi happened on several iPads that are actually mounted on my walls and therefore never "unlink" from the network. The router has been online about 20 months and I have updated all of my iPads (+/- 7) throughout the beta programs for those 20 months and I have never had this issue before. I am glad this worked and will keep it for future use but I have to think that something in IOS 15.8.3 has a specific impact on wifi networks.

Thanks for your help with this.

Any time you update a device it requests a new IP address. And connections also have a “lease time”; when this timer expires the device requests a new IP address.