My iPhone says there is no internet connection even though other devices are logged onto the internet. I’ve tried resetting my network settings which worked yesterday but not today.

Try a Forced Restart on the phone. Follow the instructions very carefully, as this is a bit tricky. You may need to repeat this several times.

Force restart iPhone - Apple Support

There are only 2 possible results when you perform a Forced Restart:

1) The phone returns to normal operation

or......

2) There is a hardware problem with the phone that will need attention at the Apple Store (make an appointment) or at an authorized Apple Service shop

Find Locations

You have already done this, correct?

Power off the Wi-Fi router

Shut down the iPhone

Wait a minute or two

Power up the Wi-Fi router

Wait a minute

Power up the iPhone

If not, this gives everything a new fresh start and a new IP Address will be issued to the iPhone and other devices.

If still no luck, the troubleshooting begins. It will be tedious. Start by disabling the Private IP Address option on the phone.

On the phone, connect to the Wi-Fi nework

Tap Settings > Wi-Fi

Tap on the blue "i" next to the Wi-Fi network name

Scroll down and turn off Private Wi-Fi Address

Then go through the same process that is already posted above

Can the phone connect to another Wi-Fi network?