But when I try to access the item vault with this character I get an LUA error:
I was able to access and store an item into my vault before, with a new character created after donation. I have some suspicion that this is only affecting this old character for some reasons. If I view the character's profile under my account in the TOME website I notice that the character's description doesn't list the official addons under its name. Somehow, the official addons don't seem to be applying to my old character anymore, despite the addons definitely marked as active in the Main Menu.