Adding on: I found the advice in the support to wait 15-20 minutes (no success) and to try switching servers to test of that works. XBOX EU is just fine and logs in, so it's not the save file. XBOX NA still causes the same error after switching back.
I play on both servers (I've made good friends on both of them, too). I have NO ISSUES logging into the EU servers, but I can NOT log into the NA servers for over half an hour (It's 3:32 PM, Pacific Standard Time, right now)! The NA servers were fine last night, 14 or 15 hours ago (maybe more?)... but not being able to collect my ESO rewards, and event tickets... may become an issue!
Last night some players were experiencing issues logging into the Xbox servers to play ESO. These login issues should now be resolved. This thread will now be closed with the issue resolved.