Note: This fix is not needed anymore. If you installed the Greasemonkey script remove it.

The games that are owned by the user aren't show as owned in the promos because games.list on the "ngStorage-user" key in the local storage is never set. It should contain the list of owned games as integers. The "userData_games" key contains the same values but in string form so you can use it to fix it.
I wrote a greasemonkey script that applies the fix automatically but I can't post links. It is on pastebin as Z6cFSnQz. You will need to refresh the promo page once to see the changes.
This also fixes the missing "in library" tag on other parts of the site but you will need to load a promo page to apply the fix. The match line can be changed so it load on any page of the site.

Edit: The pastebin link was set to expire after one month so it is no longer valid. I reuploaded the script here.

I tackled this. I would erase it, however just on the off chance that this helps any other person, this is the means by which I inspired it to work. I signed into another record on my Xbox and afterward logged retreat from it, and when I logged over into my record, the diversions showed up following a moment. I had taken a stab at resetting the comfort a few times and it didn't work, out this an attempt in case you're having issues as well.
DigitalOcean
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It works! Thank you, sugarcube! +1 ^:)

Here's a clickable link: https://pastebin.com/Z6cFSnQz

OMG, thank you, thank you, thank you! 1000+ :D

Thank you! The script works fine and I can finally enjoy the sales and promos again.

I don`t need the fix, it works for me without it. Seems, like this bug is only on some peoples account, not a general GoG bug.
But cool, that one did fix it!

No I think this is due to people not clearing cache/ cookies / site data, etc. I didn't see it either until I cleared everything stored by my browser. This issue being in local storage would also support that. If you didn't clear your browser after GOG broke it, your probably won't see this bug.

Maybe I don`t see the bug, because I never log out of GoG?

I don't know if every browser is affected but the bug is that the owned games list is not updated (in the local storage), so if you haven't bought anything since it appeared everything looks fine.

Thanks for this. I didn't use your script but you at-least pointed me in the right direction. Instead I just manually modified "ngStorage-user" and populated the array. Works fine now.

Took me a couple of min to copy the array from "userData_games" and convert it from a string to integer, then populate the games.list array. Anyone using FireFox can easily do this with storage inspector.

Manual modification done.

Thank you for these informations.

Can someone make a tutorial for chromium user? What do u have to do? I don't get it

You can use Tampermonkey with the linked script. If you don't want to install anything but don't want to do the conversion manually you can execute the function in the Javascript console in Chrome (Ctrl+Shift+J). Open the console on a tab that has the GOG main page loaded and paste the following:

(function () {const userData_games = JSON.parse(localStorage.userData_games); var games = []; for (const gameid of userData_games) { games.push(parseInt(gameid)); } const USER_KEY = "ngStorage-user"; var ngStorage_user = JSON.parse(localStorage.getItem(USER_KEY)); ngStorage_user.games.list = games; localStorage.setItem(USER_KEY, JSON.stringify(ngStorage_user)); })()

You should only do this if you undertand the code and trust the provider as it can be used to steal you account; in fact Firefox warns you about this when you try to paste for the first time. I didn't test if this works with Chrome as I don't have it installed but it should work.

If you want to do it manually then you need to use your browser devtools.

1. Load the GOG main page

2. Open the Storage tool that should be part of the developer tools

3. In Local Storage section there is the gog web address, select it

4. Inside it there are a lot of keys (the first column) and their respective values (second column) look for the userData_games key and copy its value. It should look similar to ["1","2","3"], each number is a game that you own

5. Paste the value into a text editor. We need to remove the " from the list so we end up with something like [1,2,3]. The text editor has an option for "Replace" use it to replace every " with nothing

6. In the browser look for the ngStorage-user key and copy its value. Paste the contents on the text editor in an empty document (do not mix it with the previous value)

7. The values is be long and messy but it must have a section that looks like "list": [] The brackets area might contain a series of comma separated numbers that are the games that are being curretly shown as owned. Replace the brackes, and only the brackets and its contents, with the result of step 5 so you end up with something like "list": [1,2,3]

8. Copy the results of 7 back to the ngStorage-user value

You should now have the owned list working fine for your current owned games.

Not really :-)
Thanks for the script, it's working great!

I thought it will be fixed sooner (ahem) or later by GOG but it was just too annoying...