I’ve been getting this same login error for the past couple of days with a new PS4 download/account. See ticket 200513-005447 (status: Waiting On Agent).
Have followed FAQ instructions but have made no progress:
WHAT DO I DO IF I GET A "LOGIN FAILED AN UNEXPECTED INTERNAL ERROR HAS OCCURRED..." ERROR WHEN ATTEMPTING TO LOG IN ON MY CONSOLE?
If the error persists, contact Customer Support for further assistance. Please include information regarding your megaserver, internet service provider (ISP), and Gamertag or PSN ID when submitting a ticket.
Thank you for your help!
Megaserver: North America (PS4 / Console) (also happens on EU)
ISP: Xfinity 1GB
PSN ID: Jandasdad
On Playstation 4, if you initially try to link a new purchase of ESO to the incorrect PSN account, and unlink it, you'll get this error when you try to relink to the correct PSN account. It's apparently an easy fix. It may require a second-level customer service agent with tools to handle it.
Apologies for posting in this thread originally. I didn't realize the OP (possible) server issue was unrelated and the error is identical. Actual cause became obvious after a few restless days of searching for more info while waiting in the help queue.
I updated my ticket 200513-005447 (status: "Waiting On Agent" for 4 days. This is normal I hope.)