I contacted XBOX support and was directed to make a post here to get this resolved. I purchased the Storm Island Add On and it appears greyed out on the game’s home tab which I can not access. I tried to uninstall and reinstall and still unable to access this add on.
Play through the solo mode and Storm Island will unlock with a little progression.
What’s the criteria?
It should unlock sometime after you complete the first championship in Nicé Massena. The game should play the video where the champion guy tells you about Isla de la Tempeste, then you should be able to fast travel to the docks and launch the expansion.