Wi-Fi not working

Well, if it works when connected to a different wifi network (as you stated), something could be wrong with your modem router settings / firmware.

I would contact your Internet provider and/or your modem-router manufacturer and ask them.

Take a look at this support article too:--> Recommended settings for Wi-Fi routers and access points - Apple Support

Regards and best of luck.

Giulio

Try this:

Open the wifi connection on your iPhone and tap on the "i" in blue circle at right. Then "forget his network".

Turn off your modem router and unplug it for at least 5 minutes.

Restart the modem-router and wait for its complete autoconfiguration.

Then restart your iPhone and try to reconnect it to your router, after inputting the correct password.

Regards

Giulio

Does your iphone work correctly if connected to a different Wifi Network?

If you have used the "forget this network" procedure correctly, it MUST ask you for the password.

Giulio