1. Quit any active applications that are using wi-fi or the internet (Safari, Chrome, etc)
  2. Turn OFF wi-fi by selecting the wi-fi menu bar item and choosing “Turn Wi-Fi Off”
  3. Open Finder in macOS and pull down the “Go” menu and choose “Go To Folder” (or hit Command+Shift+G to get there quickly)
  4. Enter the following path exactly into “Go to folder” window and choose “Go”
  5. /Library/Preferences/SystemConfiguration/

  6. Locate and select the following files in the SystemConfiguration folder
  7. com.apple.airport.preferences.plist

    fix macOS sierra wifi problems by trashing wireless preferences

  8. Remove those matching files, you can either place them into a folder on the desktop as a rudimentary backup, place them into the Trash without emptying, or actually delete them