Error says, server issues. I understand but can I get an update when this title will be back up.

GOG server overload due to the sale. Try outside the busy hours for your server. Have anything you can use as a download server? Like a Raspberry Pi or old laptop. Set it to download during less busy hours.

And yes, there were lots of people complaining about this yesterday in the general forum.

Only GOG may have some ideas when it will be fixed and I doubt they will share much if any information. Especially North American server(s) tend(s) to run into overload problems during sales a lot.