Octo expansion not working

Hi i have a problem with my octo expansion i got it 2 days ago from the eshop and i paid 20 dollars for it and then went to my Nintendo switch main menu and it shows 2 splatoon games do i waited for the download and it says i have to download software to play and went to the eshop again and it says i need to buy splatoon 2 again btw i bought from the game as the card for it so i am not gonna pay 60$ for game i already have so i need so help from anyone who knows how to fix this please 🙏