Unable to Login to EA with secondary Xbox account

[HellerCat]

The PvZ GW2 offers a local multiplayer and local co-op that does not require Xbox Gold.

However, when I try to log in to the game with a secondary Xbox account (my son's account), either to play the game in a single mode or as a second local player, the game will ask me to log in to EA again. When I try to log in, with a new account or the existing EA account, the game simply says "Unable to Login".