I have the same problem. Looking into the installer's certificate, it seems to be valid until January 2018 (?!), and I believe this is the reason. Possible solutions which are working for me: turn off driver signature enforcement, this works with both signed and unsigned installers of com0com 3.0 for me. use com0com 2.2 signed installer, this one gives me a popup to trust the author when starting the installer, and everything works afterwards. Since I didn't want to turn off a Windows security feature,...
Same issue here, however in-between it only says "Cannot download repository.txt"...