Hey there @Nennee,
Apologies for the delayed response but good to see you've had some assistance already.
Yes - you must have Ubisoft Connect installed to be able to access and play your library of games.
If you own the game via Ubisoft Connect and you're signed into the correct account, you'll be able to purchase and the access the WONY Expansion from the Ubisoft Store without any issues.
If you do ha...