For some time now (ca. two weeks) GoG Galaxy is no longer showing activity for any games, including those purchased from gog.com.

The activity feed of every game is blank, and an error message is displayed at the bottom: "Sorry, we couldn't load the data."
There's an option to retry, which doesn't fix the issue.

I tried to re-sync integrations, but that also had no effect.

Any ideas as to what caused this/how to fix it?

Having the exact same issue. Not sure how to fix it.

I've been having this issue since the update before the current one, with no fix in sight and nothing I do fixes it. Activity is at a standstill and it appears to have stopped recording GOG achievements, as well, though I'm not 100%.

This is a month old problem for me, going back to just after Thanksgiving or thereabouts.

This fixed it for me. I should not have to have my profile enabled to track times and achievements, but I guess as long as I can set it to "Only me" then GOG can have its way on this.

My activity feed has been frozen for a week now. None of my own activity or any friend activity has updated. My profile is public and has always been public.

Thanks, @bratmaxe, this worked immediately.
For reference I entered:
settings in GoG Galaxy > Integrations > GoG [Manage] > Privacy
and checked "profile enabled" with all subsections set to "only me"
The second I did that all the games began displaying activity again. Not sure why that was the case, as I didn't touch this setting before.
Still, thanks again for the solution :*

I guess my issue is different. My activity feed shows previous entries. Instead of being empty like yours, it just stopped updating 7 days ago. No new achievement notifications or playtime updates from myself or anyone else on my friends list.

This really shouldn't be marked as solved. I don't even have a profile enabled in my settings, yet Galaxy is happily spamming away "Sorry, we couldn't load the data. Retry" for every GOG game I own. This needs to be fixed.

I don't understand your solution. What do you mean by "all subsections still set to private"?
Is this a setting in the GOG Galaxy app or on the website? Because the app doesn't actually have any privacy settings that I can see.
So I looked for what you are talking about in the website. The closest I could find was settings->privacy, but I cannot find the "private" option in privacy settings for any of the subsections.
Speaking of subsections, are you referring to each of the sections underneath "Profile, Friends, and Chat"? Or does that include under "Wishlist"?
Also what do you mean by "disabled my public profile"? There is a check box for "Profile Enabled" and also "Visibility". Is that correct? Should I do anything to visibility?
Sorry for all the questions. I really appreciate any help!

Not quite a solution, because I can't exactly give it to you step-by-step, but after going to the Privacy & Settings line (GOG website, menu bar, username, scroll down menu) and checking and unchecking the things as suggested, it still did NOT work for me.

THEN I figured I would DL & reinstall the GoG for Windows. When I tried to install it, it said I still had it running, and I should close it. Strange. So, I looked in Task Manager and terminated an instance of what was indeed running. After that the installation continued and immediately terminated with a "you are already up to date" (sort of) message. BUT now I CAN install and update all the games in the GOG for Win!

I have no clue why this worked for me, but it did.

My solution simply meant to re-enable the public profile in case it was turned off.

But don't bother with that, GOG seems to have fixed that anyway. Activity is now displayed regardless of the privacy settings. If it still does not work for you, this might be a different problem or bug.

Edit: To clarify: The "Public Profile" setting I was referring to is the checkbox "Profile Enabled" under "Privacy & Settings" -> "Privacy" on the website. You can access it on Galaxy too by clicking your avatar -> "Account management" -> "Privacy".