You must be an Administrator on your Mac to enable SharePoint Online sync.

If you're using the OneDrive Mac Store app, uninstall it.

Install the latest build of OneDrive for Mac.

Exit the new OneDrive sync client by clicking on the OneDrive cloud icon in the Menu bar and selecting Quit OneDrive.

Open a terminal window and run the following commands:

Defaults write TeamSiteSyncPreview -bool True

Defaults write Tier Team

Killall cfprefsd

Restart the sync client and log in again if prompted