If I win a giveaway but don't receive the game can I enter giveaways for the said game again?

So I won a giveaway 4 days ago, and I just now realised that the giveaway maker made an account 4 days ago, and hasn't been online since then (probably doesn't understand the rules, forgot about the site, or is not interested anymore)

If I don't receive the game after 7 days has passed and mark it as "not received " can I enter giveaways for the said game again after that (after 7 days)?
Or I can never enter giveaways for that game again, because it says I won it (two wins in an account then?) Will it still say I won the game after I mark it as not received?

Also should I try to add the giveaway maker on steam or just wait a bit more?

And before you ask no, I haven't found this info nowhere in the FAQ.