I've been getting the same problem the last few days (South Australia)

It's been affecting me too.

Australian user here too.

Third day in a row for me.

I just tried using my VPN to connect to USA servers on my Mac Book Pro and the problem went away.
It seems to be an Australian issue. Are other countries experiencing this problem?

Using a USA server for VPN only slows the internet speed but makes you look like your connected in the USA.

We know COVID-19 is slowing things down when it come to customer service, so we may need a good dose of patience. The website still functions and the installed games run. So we can be grateful for their no DRM policy. At least most of us still benefit from their forums giving us a chance to let off some steam.

@iconicalfrog suggestion the OP for https://www.gog.com/forum/general/is_gog_galaxy_down_1/page1 I am posting workarounds for this odd error.

Currently, you can install your games from an offline installer on the website and run them from their exe files. Also, updates can be applied in old-school style as patches from the website. You'd be missing cloud sync, game overlay, chat ... but most (not all) games multiplayer work without Galaxy.

@chrustec reports that the broken Galaxy 2.0 can still download updates for imported games while the offline error messages displayed.

Here are the workarounds, not solutions as Galaxy 2.0 is still broken in some geolocations:

A) Use a VPN that moves geolocation outside of AU to US for example.

or

B) VPN + Split-tunneling would work since GOG Galaxy client doesn't need a lot of data transfer, keeping the open channel for the game itself. I haven't tried this approach but it's worth a try keeping your gaming at low latency and higher bandwidth.

Here is how to do it on Windows 10:

https://www.howtogeek.com/526092/how-to-auto-connect-to-a-vpn-for-specific-apps-in-windows-10/

It's easier to do with OpenVPN modifying your client config file but you'd be targeting gog.com domain instead of the GOG Galaxy app. Add the following two lines:

route-nopull
route 77.79.249.90

or

C) Install the old Galaxy client v1.2 with auto-update disabled. I can confirm that this works, as it probably gains access to the GOG backend differently. This workaround should do at least until GOG Galaxy devs get to the bottom of this problem.

It works for those who don't like offline installers and more importantly for those who have already installed games and want to continue syncing their saves after importing them back into that old client.

1. Uninstall Galaxy, then download and install the old client hosted on GOG https://content-system.gog.com/open_link/download?path=/open/galaxy/client/setup_galaxy_1.2.67.58.exe
2. DON'T let Galaxy start after the setup (untick the box).
3. Delete C:\ProgramData\GOG.com\Galaxy\redists\GalaxyUpdater.exe
4. Right-click the shortcut, properties, "Target" box, append a space and "/runWithoutUpdating" at the end (without quotation marks)
5. Disable Galaxy autostart in settings on the first run

Credits to OP BlackSun for the downgrade method:
https://www.gog.com/forum/general_beta_gog_galaxy_2.0/how_to_keep_galaxy_v12_client_and_avoid_the_forced_v20_beta_update/page1

Finally, I opened a ticket already, no worries, and it was assigned to GOG Galaxy dev team too.

GalaxyClient.log
Once connected to VPN in the US and another with bare internet or using a VPN located in Melbourne.
Connection from AU:
2020-10-21 22:10:20.805 [Warning][ (0)] [TID 2200][galaxy_client]: Failed to check API status. Assuming it's offline.
connection with VPN geolocation to US:
2020-10-21 22:11:28.349 [Information][ (0)] [TID 18856][galaxy_client]: Successfully checked API status: Online

I dug around in the python script for Galaxy on Github. I suspect it is an issue with the chromium embedded framework (CEF) version in the latest Galaxy client, but an expert opinion will tell. Oddly the old client's CEF is OK. Why it doesn't play nice in some geolocations beats me?! but my guess it has to do with ISP-level filters.

This security issue might be related to the problem too:
https://developers.googleblog.com/2020/08/guidance-for-our-effort-to-block-less-secure-browser-and-apps.html

A friend in NSW experienced this on their laptop on their work network, but not on their home network. I found that quite curious.

Home network might have an outbound VPN or something set up on their router?

I'm in Indonesia and I got the same message too.

Thanks I did this solution and I can now download and install games. I prefer this to getting the offline installers as Witcher 3 has 10 separate files to download!

I'm down in Tasmania and same issue here. I managed to get a support ticket opened as I couldn't install Outer Worlds so I've sent a link to this forum to them... Hoping they fix it soon!

I live in Italy and I can confirm the same issue, but when it manifests the entire GOG site becomes unreachable without a VPN.

I just got an update from my ticket

"I apologize for this inconvenience and ask for your patience, since we're working on resolving this problem."

Hopefully it's fixed soon

I got the exact same reply to my ticket today

Yeah still offline for me and it's been 3-4 days now :O. Hope they get to the bottom of it soon. I'll keep the downgrade solution in mind in case I need to use it. Thanks to those posting the helpful posts in this thread.

It seems to be working again for me