It could be that your device doesn't meet the system requirements for the story mode. Or, there might be some compatibility issues with your software or hardware.
Maybe there's a technical glitch or your game version isn't updated. Check for updates and see if that helps.
There could be several reasons. Maybe your game installation was incomplete, or there's a problem with your internet connection if it requires one for the story mode. Also, it's possible that you haven't unlocked the story mode yet by fulfilling certain in-game conditions.