Maintenance for the week of April 6:
• [COMPLETE] ESO Store and Account System for maintenance – April 8, 9:00AM EDT (13:00 UTC) - 6:00PM EDT (22:00 UTC)
Nevermind. I discovered that if you go to Bethesda's website, select HELP, pick Elder Scrolls Legends as the game, search for "doom wolf mount", it will take you to a page about it. Somewhere in all this I found a link which indicated I could go to my account and have it show me the code. I did this, found the code, followed the link, redeemed the code, and it added the mount to my account. Wish I could recall the exact sequence but this is roughly what worked.
Shout out to ZOS support for making me wait 5 days just so I CAN'T get the mount because they didn't read my ticket. Thanks wasting 5 days just to finally answer my question.