Previously won game shown in All giveaways

Same issue for me here too

Even after sync ?

Have you synced your account to steam? It knows you've WON the game, but sounds like they don't know you also activated it. You still have to sync your account to make recently won games hide themselves, as far as I've noticed.

If you have the option here set to hide games you already own, it should remove the game from the giveaway list so that you don't see it.

If you disable that option and click on a game that you already own, the enter button should say "Exists in account" and not let you enter.

With the new change here, giveaways should say "Previously won" and not let you enter of you have previously won the game.

Since you are seeing "Previously won" and not "Exists in account", I believe that means that the site sees that you won the game, but it does not see that you own it on Steam. Looking at your list of games on Steam I see "Wolfenstein: The New Order German Edition". Maybe the German edition has a different Steam ID from the standard version which is causing SG to not see it as existing on your account and showing you the wrong notification on the giveaway enter button.

I had the same experience with Layers of Fear which i won yesterday, even after syncing.