From support:
Hello there.
Thank you very much for contacting us.
We're sorry to hear you are having trouble with the downloads of your games. Based on your description, it looks like you may have been affected by a recent issue on our side.
We are currently experiencing some disruptions in our backend services, which are preventing GOG GALAXY and GOG servers from retrieving game data and initiating downloads properly. Since the problem is server-side related, it is not caused by your device or setup.
We are working on fixing this issue so if possible, please give us a bit of time to have everything sorted our from our end and soon, the ability to download and install your games should be restored.
Apologies for any inconvenience caused and if you have any other questions that you would like to ask, then feel free to reply to this e-mail and let me know.