No internet after uninstalling Norton 360

Do the following: boot into Safe Mode according to How to use safe mode on your Mac and launch the shareware app You can check to see if you've removed all of the supporting files by downloading and running the shareware app Find Any File to search for any files with the application's or the developer's name in the file name.  For Norton software you'd do the following search(es): 

1 - Name contains norton

Any files that are found can be dragged from the search results window to the Desktop or Trash bin in the Dock for deletion.

FAF can search areas that Spotlight can't like invisible folders, system folders and packages.  

cornelis160 wrote:

I used RemoveNortonMacFiles.zip to remove Norton 360. After that my MacBook Air did not connect to internet, however in Safemode it did. Searching for 'Norton' by 'Find a File' showed that many Norton files were not erased. After sending these to the bin, it transpired that NortonForMac.kext could not be deleted. I could neither delete the files using 'sudo unload' and 'sudo rm' commands in terminal app. Then I discovered that Norton was still active in the System Preferences Network window when in normal mode, while in Safemode it was not connected. After removing Norton from the Network window, the problem was resolved. 

Uninstall all third party apps that are Cleaners/Optimizers/VPN/Anti-Virus

all known to cause issues on the macOS

macOS - Security - Apple macOS - Security - Apple

Apple Platform Security - Apple Apple Platform Security - Apple Support

more—https://manuals.info.apple.com/MANUALS/1000/MA1902/en_US/apple-platform-security-guide.pdf