As a general rule, if one download method doesn't work for you, try a different one. We offer two download methods here at GOG.COM - these are:
GOG GALAXY - our optional client which offers easy installation of games, automatic updates, as well as downloading standalone installers with full protection against download corruption.
Browser downloads - the oldschool option, which lets you just download standalone installers onto your computer, and install them anywhere, at any time.
If you would like to learn more about these download options and how to use them, you can find a more detailed explanation and instructions in this support article.