Was able to get a cached version of the page, it looks like the people running that site took it down.
Here is the Mega Link: h++ps://mega.nz/?#!udBDyTTb!wpF1VjwJtnd0I2b5F12ZovjvoJXyyjwyLJZseSTn2aY
This is the description:
> An experiment in sissy self hypnosis and Pavlovian conditioning.
> This game is a proof-of-concept for an immersive alternate-reality game wherein the player becomes the player-character in their own M2F transformation fantasy journey. The 21 Day Challenge is designed to mimic the appearance and nature of many of the popular sissy hypno devices from games like Whoremaker, Perverted Education, Escort Dreams, Psychology Club, Secretary etc. only with the players' computer becoming the hypno device directly and the player themselves becoming the character being hypnotised. It is designed to be played over a period of 21 days, and should remember progress even after browser restarts and computer reboots (Note: DO NOT PLAY IN INCOGNITO MODE).
> The content is tailored to become more intense as the player progresses, so any real-life changes which begin to occur while playing will only become more pronounced as the story continues; if this begins to take you down a path you do not wish to travel, stop playing immediately and delete the file. This constitutes the only form of fail-state which is possible with this kind of game: the voluntary cessation of gameplay.
> All images, audio, and video used are considered to be in the public domain, and all credit for the original multimedia content goes to the respective creators (too numerous to list).
Most likely OP used some newer zip compression options. Using the newest version of 7zip (2018/04/30), the files extracted correctly. Zip is 8GB though, so I think you need the paid service from Mega to download it (Someone else can split it up if its worth while)