Iphone 13 says it's connected to wifi and mobile data, but then says "network not available" when I try to open an app

My iphone is showing the fan saying it's connect to the wifi. But when I try to open an app, it just says "connecting" and can't open it. All other devices are connected to the wifi fine.

I've tried restarting the phone several times. I've also tried turning off the router and on. Also forgetting the network and reconnecting to it. All to no avail.

When I turn off the wifi and try to use data instead I get the same issue, so it's something to do with my phone's connectivity.

Any advice on what I can do?