https://www.esoui.com/forums/faq.php..._howto_install
You should be able to find the correct folder for your addons like described above, else login, take a screenshot via keybind and check the top right edge of the screen. The patch the screenshot is saved to is the path where your AddOns folder should be in!
Or: Search for AddOnSettings.txt or UserSettings.txt on ALL harddrives/SSDs and check which one got the most current "last changed date and time" -> correct folder then.
Attention:
If you extract the addon zip files be sure to ONLY extract the content's folder and do NOT create a folder name same as the zip's name!
Filename given is e.g. "TheElderBar_v5.zip"
Wrong:
c:\users\...\documents\elder scrolls online\live\AddOns\
TheElderBar_v5\TheElderBar\TheLEderBar.txt
[u]Correct:
c:\users\...\documents\elder scrolls online\live\AddOns\TheElderBar\TheElderBar.txt
If this all does not help we need more info OR you need to search for OneDrive in the official ESO forums e.g. (if you use it) and disable it for ESO/documents.
But one of the above mentioned hints should lead to a properly working addon folder and setup for you + maybe some more reasearch by forum threads/search by yourself here.