Maintenance for the week of May 25:
• PC/Mac: No maintenance – May 25
• ESO Store and Account System for maintenance – May 27, 6:00AM EDT (10:00 UTC) - 4:00PM EDT (20:00 UTC)
Might wanna test one or the other to see if that resolves the issue. I briefly recall getting an error similar to this at some point the other day in the midst of testing a bunch of other unrelated stuff, but I think it went away after a reloadUI.