iPhone only gets IPv6 DNS fe80::1 and nothing else

Sorry, but I want to make sure I understand your answer. Are you saying that your iPhone cannot connect to any Wi-Fi network?

If so, then as you stated, you have already tried resetting the iPhone's network settings ... so we only have one option at this point ... and that is to restore your iPhone.

To do so:

• Connect it to your computer.
• When your iPhone appears in the iTunes source list, click the Restore button on the Summary tab. (Note: This will erase all of your data and media, and then, resets all of the iPhone's settings. You will need to restore it from a previous backup from either iTunes or iCloud.)

No problem. I understand completely now. Thanks for confirming that for me.

There are two other possibilities:

1. You have enabled Time Access Control on the AirPort Extreme and the iPhone's MAC address has been added to the restricted access list.
2. Your 4th generation AirPort Extreme may be failing. This model came out in 2011. Most consumer-grade networking hardware have a typical lifespan of 3-5 years ... but I would think that with the other devices not having any issues getting IPv4 addresses from the base stations DHCP service that this shouldn't be the case.

With the second item, you can try updating the DHCP lease on your iPhone, as follows:

• Settings > Choose "Wi-Fi"
• Find the Wi-Fi network that you want the iPhone to connect to, and then, tap on the info icon.
• Under the DHCP tab, scroll down to reveal the "Renew Lease" option and tap on it.
• All network fields should clear out, and then, refill with the appropriate addresses.
• Close Settings.

Can you iPhone connect to other Wi-Fi networks, just not this one? If so, which model of the AirPort Extreme do you have?

You're very welcome! I'm glad you got it worked out ...