iPhone wifi not working

My iPhone XS wifi won’t turn on. The actual slide button and the button in the control centre shortcuts won’t stay on. It sometimes briefly goes on but doesn’t connect to wifi.

So far I have tried all fixes that were suggested online:

- Reset network settings

- Reset the router (my iPhone 7 is having no problems connecting to the same router.)

- Cleared all settings on phone

- Turned phone off and on

I have done the above several times over the last few days, and no luck. Wifi simply will not turn on at all. Nothing to do with connectivity.