The issue is users wanting the freedom of online play without hindrance. An offline play button will not allow the user to choose a mod pack to play with, if the download server has not displayed information about the mod pack in question, even if the mod pack was already downloaded.

What are you trying to do? make sure paid users get the mod packs? We need added authentication like a hole in the head.

You must separate the download/install action controls from the game launcher controls, else this issue of unreliability will just continue.

People are resorting to another launcher like MultiMC because they can not use the FTB launcher when they need it to play the game.

Making the user go through 2 different servers (FTB download/install/update server and Minecraft authentication login server) before they can play the game online is superfluous.

One possible suggestion: Write a function to check for mod packs already downloaded and indicate these mod packs were already downloaded in the mod pack choices before connecting to the download server. This way if the download server is down for any reason the user can still go online choosing what is already installed and play the game.

Do not delete my posts unless you delete me as well.