Possible causes include wrong ESO folder, case-sensitivity and file permissions. See bellow for how to debug them.
First you need to make absolutely sure that is the correct ESO folder.
Do you have an UserSettings.txt file in "~/Documents/Elder Scrolls Online/live/UserSettings.txt" ?
If yes, make sure it is loaded:
1) close game
2) make an obvious change in it, for example set it to play or to skip intro videos by changing both these values to "1" or to "0" respectively:
SET SkipPregameVideos "1"
SET HasPlayedPregameVideo "1"
3) open game and observe if your changes are applied (do you see intro videos?)
If the changes are NOT applied then that is not the correct folder and you need to find it (don't know how...)
If however the changes are applied then it might simply be a case of case-sensitivity for file names (had a similar issue a long while ago with Fallout 3). Try to rename an addon and all its files and folders to lower case only and see if that helps.
Another thing to do: create a test addon with the following:
- cd <addons folder>
- mkdir testaddon
- echo "error('it works')" > testaddon/testaddon.lua
- echo "testaddon.lua" > testaddon/testaddon.txt
- start game and login; you should get a lua error with text "it works" if... well if it works
Last: file permissions. Change all folder permissions to 0755 (user: all, group/others: read/list) and all file permissions to 0644 (user: all, group/others: read only) via the following:
- cd ~/Documents/Elder Scrolls Online/
- find . -type d -exec chmod 0755 {} \;
- find . -type f -exec chmod 0644 {} \;
Relaunch the game and see if it helps.
I hope it helps. If not, please report back and we'll take it from there (I have some more ideas, like intercepting "open()" syscalls).