Thanks for the feedback Roidal. I’ll get in touch with Humble again and see if they can get this fixed.
Tim
Today i have good news:
Download is available now. 
That is good news Roidal. Humble have been in touch and it seems they’ve managed to fix it but I still don’t understand the underlying problem. It seems to occur every time we upload a new build.
cgmoo, is it working for you now too?
New situation: It is possible to download the MM-Addon, but not the base-game at humbleblundle.
Thanks Roidal. It’s the same issue. I just don’t get it. I’m looping in my publisher so he can contact them.
EDIT: Well not quite the same issue. As you point out this time it’s the base game that doesn’t work. 
Just checking, this is the linux build right?
Sorry for late answer,
yes iam talking about the linux build
but meanwhile its available again.
Thanks!
I was also facing the same issue, its helping me out at some points but somewhere I have to rectified these problem by my self 
,… anyway … thanku …