I'm posting this for a friend but this happens to everyone I meet. As the summary states of the pack is too large or there are too many Minecraft WILL NOT load it. There used to be a small fix on Xbox where you would open games and apps and close the menu really quickly but then it stopped working. This has been in the game for years and if the argument is that you should use smaller or larger packs then why not set a limit on the amount of megabits one can use. It effects marketplace maps, add-ons, texture packs, and everything else. I might not respond immediately but I will check every few hours to see if there is a response.