my iphone 14 pro has stopped responding to wifi

Here’s more VPN information: VPN frequently creates more problems than it solves. But one important fact is that when you install VPN it configures itself to the specific hardware, iOS version and network that the phone is currently using. If any of those change (such as updating iOS) it can break the VPN. So any time you change any of these you may need to delete the VPN app and profile, restart your phone then add them back (if you still want to use VPN) so it can configure itself to the new environment.

Here's Apple's advice on VPN→

Check VPN (Virtual Private Network) and third-party software to help resolve network connectivity issues - Apple Support

Something to think about→Don't use VPN - GITHUB

If you really did reboot the router, most likely it is a hardware failure of the phone. Rebooting the router is an important step, because routers have a failure mode where they can stop connecting to only one device, and still work for a dozen other devices.

Also, if you have VPN on the phone that can prevent it from connecting to Wi-Fi, so if you do delete the VPN profile.

Does it work on other Wi-Fi networks? That is the real test of whether or not it is the phone.

Restart your router by turning it off or unplugging it (if it doesn’t have a power switch) for 15-30 seconds.