This is a bit of a doozy...and I am entirely flabbergasted. As the title states, my child's XBox Gamertag cannot play Minecraft online on the 360, but my account can play online just fine. Just a quick rundown...
I also have Minecraft for XBox One, and my child's account can play online just fine on that.
I have XBox Live Gold, and my child's account is linked to mine.
My XBox 360 is set to 1080p.
My child's privacy settings are set to allow for online play.
All content restrictions are off.
Please, for the love of god, does anyone have any suggestions?