This is not AddOn related or caused:
We hat this on the PTS a few months ago already, maybe ZOs re introduced the bug...
The addons you enable pre-game (At character selection) and ingame (via the addons menu) are stored in the file live/AddOnSettings.txt
The entries got some headlines whichd escribe which server and character you configured the addons for, and one #Default which is the "All characters" from the character selection screen.
On the PTS there was a problem that some character names were written in CAPITAL LETTERS and thus the game did not find them anymore.
As my addons all still work properly and my AddOnSettings.txt looks normal, like #EU-Megaserver-Baertram, I asume this only happens to a few users now where there are special characters or spaces in the character names.
I'd do the following:
Logout, add the file live/AddOnSettings.txt to your antivirus whitelist/allowed files, explicitly!
Backup the file!
Check this file live/AddOnSettings.txt if it got a readonly tag. Right click it -> properties -> remove read only checkbox if it is set.
Check the contents of the file if the server and character names are shown properly, and not all UPPERCASE e.g.
Repor the issue to ZOs officially via /bug ingame and the forums here.
I bet someone did already.