wifi doesn't have a valid IP configuration

Starting about a week ago multiple devices in our house starting failing to access the internet, intermittently. Signal strength is good and, when I can check, data speeds are great. But various computers (Windows 7, Windows 10, Windows 11) [Edited: "Language"]. And then work at other times.

We've now gone through 3 modems and no real change.

In doing some further investigation, it seems that, in all of these cases, the ipv6 sites work, and it is the ipv4 sites that fail.

Looking at the wifi adapter properties, I see "No internet access" for ipv4, with ipv6 working as expected.

Further, I have an extender taking in one of these problematic signals, However, if I connect to the output signal from this extender, things work, and I have ipv4 access. It seems that the extender is reconditioning the problematic signal from the Xfinity gateway.

This happens on both 2.4GHz and 5GHz.

I hit the Diagnose and I see a message:

"'Wi-Fi' doesn't have a valid IP configuration."

I've changed nothing to cause this, but think it may be related to some recent Xfinity change. Any ideas on what's going on/what can be done?

(And getting my owe Gateway is certainly an option, but I want to give Xfinity the chance to fix this since it seems unlikely to be my issue across multiple devices."