However, as soon as you do get to the Isle of Armor, you'll be challenged by one of your new rivals: Avery if you're playing Pokémon Shield or Klara if you're playing Pokémon Sword.
Once you've met these conditions, you'll be allowed to make the trip to the new DLC area. You'll need to be able to travel to Wedgehurst Station, and you'll need to have access to the Wild Area. If you haven't beat the game yet, you might still be able to travel to the Isle of Armor as long as you've made enough progress. See, if you've already beat the game, you'll have no problem getting there.
Once you've purchased your DLC Expansion Pass and your game has finished updating, you're probably ready to head off to the Isle of Armor.