Can't connect to 5GHz Wifi

My 5s can connect to 5GHz networks just fine, so your 6 should also. I'm on 11.3.1.

You could try resetting your network settings - whenever I have odd internet behavior, that's something I try. You will have to re-enter any wifi passwords.

"Go to Settings > General > Reset > Reset Network Settings. This also resets Wi-Fi networks and passwords, cellular settings, and VPN and APN settings that you've used before."

That quoted bit is from the article below.

If you see No Service or Searching on your iPhone or iPad - Apple Support

~Lyssa

Do you have different names for your 2.4 GHz and 5 GHz bands? If not, that's a good way to assure that devices will always choose 5 GHz if you use that band's name. If the names are the same the device will choose the band with the stronger signal.

A couple of things you should try (you may have already, of course):

• Restart the phone: Restart your iPhone, iPad, or iPod touch - Apple Support
• Tap the i next to the network name and forget it
• Settings/General/Reset - Rest Network Settings
• Restore iOS using iTunes on your computer (make a backup first, of course)

I did NOT lose 5GHz connectivity on either of my iOS devices after upgrading. If it was a problem with the version there would be thousands of posts about it and articles in all of the trade publications as well as tech columns In major news publications. Wait if you want, but the probability of the next release fixing it is vanishingly small.

BTW, have you verified the problem with other 5 GHz networks?

You would have a much better chance of fixing it if you contact Apple Support using the link at the top of this page.

Are the other iOS devices in your house on iOS 11 or are they running an older version?

Have you restarted your router lately?

~Lyssa