Not being able to enter worlds or servers and missing twitch files

I have re-downloaded the launcher and re-installed the game on my pc, but I still can't play the game at all, as well as not being able to find the twitch broadcaster. Either when I start the game or when I join a server/single-player world, the game freezes on downloading terrain and then crashes, or sometimes just stays unresponsive without crashing. I don't know whether the crashing is as a result of the game not being able to locate the Twitch libraries or not, which is why I am reporting both instances in a single bug report.