Same here since the update to 9.8.0.0, even when starting the game first and then HearthRanger with admin rights. The bot can read the decks, so the game appears to be connected but it keeps harping to "Please start game".
I started the bot right after the update while still in a Tavern Brawl, then set a queue (do coupla Tavern Brawls first, then Unranked Plays for the 100 G) and hit the play button to take over. However where I am used to seeing the game types as "Ranked Play", "Unranked Play", "Arena" aso, it now labels them as "Play_Casual", "Play_Ranked", "The_Arena" aso. Does that help to diagnose?