https://www.esoui.com/forums/showthread.php?t=9149
First creenshot, top right edge.
Enable the checkbox.
If the list of addons is empty you need to check your antivirus, windows updates, Microsoft Onedrive and Microsoft Defender.
Whitelist the c:\users.-...\documents\elder scrolls onlien folder in them
Remove your documents frolder from OneDrive as ESO does not support this!
Login once and change some settings of the game, exit again.
Search for the file UserSettings.txt on ALL your harddrives and check the one with the date and time of last change where you were logged in the last time.
The folder where this file lays shoudl contain an AddOns subfolder where your game wills earch for the addons now.
Don't ask me why but sometimes ESO will just all of sudden search and save inside the folder c:\users\...\AppData\ instead of c:\users\...\documents
Maybe it happend for you as well.
If so: Use /bug ingame and tell ZOs about it! Be patient and reply to their first email and tell them you need additional help and tehy will look into it then.
The more tell the same problem the better the chance to get this fixed.