Seems that you have been lucky not to get yourself banned by using someone else's Account.
You should always use your own Accounts.
The game was purchased and is locked to that other person's Account, the game would be in their Library for them to download.
It will not show in your Library as you have never bought it for your own Account.
To play the game, you need to purchase it for your own Account.
If you do cut corners and use that old Account of the Sellers, then eventually, you could be faced with a ban and or a console ban and nothing will work online.
For the sake of a bit of money, get the game for your own Account and keep safe.