Forza Horizon 2 Digital copy won't transfer to my friends account

Forza Horizon 2 Digital copy won’t transfer to my friends account
I have bought it about a month ago and my friend can’t access it Why
I have contacted Xbox Support and they told me to come here
Its is the support code from xbox one support:
1343750703

I’ll try and explain this.

If you buy FH2 on your xbox under your gamertag. I assume then you put your gamertag on his xbox and downloaded the game to his xbox. However, the game is still tied to your GT and not his. He can not play the game because he didn’t purchase it for his gamertag.