Someone posted already above about pressing “Play” quickly. If you go into Hearthstone (where you pick decks), it forces you to choose a free deck, and you already know the story: it doesn’t work.
When the match starts, you just need to restart the game, and you’ll be placed directly into the last match. Finish the match, and when you return to the hero selection screen, that popup should be gone.
This will let you pick any deck you want to play with, but if you go back to the main menu and return again, it might show up again (it happened to me, and then I repeated the trick).
I tried that - switching back and forth. between regions. but I’m in US and tried changing it to EU and Asia. No luck. glad someone gets to play at least