Original Post — Direct link

I receive a "Deck Authentication Failed" message while trying to enter the Historic Ranked BO1 queue. After testing what was causing the error by removing the new Historic Anthology 3 cards (no issue), I determined that it was my companion, Yorion, that is causing the issue. I cannot queue in the ranked room with Yorion as my companion.

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almost 4 years ago - /u/wotc_kale - Direct link

See if you have 16 cards in your sideboard. There is currently a bug in which we don't warn you when you have 16 cards in your sideboard (including the companion).