Looks like the official Messenger Plus 2 beta download site is down. But have no fear, there are already mirrors up and running for you.
North America: Mirror 1 | Mirror 2
United Kingdom: Mirror 1
Netherlands: Mirror 1 | Mirror 2 | Mirror 3 | Mirror 4 | Mirror 5 | Mirror 6 | Mirror 7 | Mirror 8
Belgium: Mirror 1 | Mirror 2 
France: Mirror 1
New Zealand: Mirror 1
Australia: Mirror 1 | Mirror 2
Norway: Mirror 1 | Mirror 2
Israel: Mirror 1
This should do it for a while, Thanks to GZ for giving me the info and iiez for listing the mirrors.
Note: The content of this post is over 4 years old. Feel free to share your refreshing comments.
