Internet not working after macOS High Sierra upgrade

I followed all the instructions from others and they did not work for me.

Here is what I had to do to get my WIFI working again:

1. Go to /Library/Preferences/SystemConfiguration
2. Delete ALL files that had been modified today (only one file was not which was com.apple.Boot.plist).
3. Rebooted the computer.
4. Once rebooted, I had to reconnect back to my WIFI.
5. Everything worked after that.

I hope Apple will do better testing in the future before rolling out a patch.

I tried all of the reboots and deleting preferences, but they all stills resulted in issues - mine was saying there was no wireless hardware found at all. The thing that finally fixed it all was rebooting while holding Command+Option+R to do internet recovery (where I noticed my Wi-Fi was working just fine), then reinstalling High Sierra. I noticed when I reinstalled, it took significantly longer than the first time, so I have a feeling that it didn’t install correctly the first time.

I tried every fix i could find on the forums including reinstalling osx, flushing dns cache, trashing preferences, deactivating deleting and re-adding wifi to network preferences and i still kept getting a combo of either : wifi wont turn on, hardware not installed message or wifi working for up to an hour and then becoming unresponsive... was starting to think it might be hardware issue and give up after two days of troubleshooting... then as a last resort i not only reset the modem and airport, but renamed the airport... since then all is working perfectly! I’m not sure exactly what fixed it, but if i had to guess, somehow the network files regarding the airport got corrupted during upgrade to high sierra... it seems too simple to just change the name yet thats when it worked properly and lasted... the smc & pram resets and deleting preference files gave me only a temporary fix - not more than an hour of wifi and then back to tge problem... i really don’t know...

All devices are using wi-fi internet without a problem, except the Mac Pro after HS update.

Tried all options here, but the only thing that worked was renaming my router, then un-renaming it. Seems fine now.

Wifi was saying no hardware installed, refusing to turn on, and when i could get it to work would become licked in turned off state unresponsive... I spent the past few days trying everything from reinstalling osx, deleting preferences, reset smc & pram, you name it... what finally worked for me was to reset and rename my modem! Since i have connected to newly named airport wifi has been working fine...

I found I WAS still getting wifi, but couldn’t access any internet sites. I also use a VPN. I had to disconnect from it then install upgrade for VPN. ie your VPN may be the culprit.

On your Mac, select from the Finder Menu Go -> Go To Folder… and type in the following path. Hit Go.

/Library/Preferences/SystemConfiguration

Delete the following files in the SystemConfiguration folder. You may be prompted to enter your Mac OS X password.

com.apple.accounts.exists.plist

com.apple.airport.preferences.plist

com.apple.network.eapolclient.configuration.plist

com.apple.smb.server.plist

NetworkInterfaces.plist preferences.plist

1. Empty trash.
2. Restart your Mac.
3. Everything should work now!!!

Sadly, I tried the "SOLVED" response posted by francioscarrier two days ago, and alas, experienced the issue again this morning. We're having the issue on several of our machines at work, and it is definitely related to High Sierra. No issues were experienced prior to the upgrade, except on the 3 new machines, which I believe came pre-loaded with HS. Working with Apple Support now, but I'm not optimistic.

Try power cycling your router.