what can i do???

this is the giveaway, I dont have access to it
https://www.steamgifts.com/giveaway/R0wDL/on-board-4-pc

Have you tried poking them on steam about it?

Edit: For future GAs, it would be better to contact them first to figure something out before marking the GA as not received.

Just move on. This is not the first giveaway this creator didn't deliver and it probably won't be his last. If he blacklisted you without contacting you to see what's the problem he obviously doesn't care about having not received feedback on his profile.

Did you tell them that the key was duplicate? If you ever get a duplicate key, that's the first thing you should do, and then it's up to the giveraway creator to get you a working key.

You cannot press Not received for an entire week after the giveaway ended. Meaning, you pressed it after waiting an entire week without uttering a single word about your issue to the giveaway creator, since the giveaway comments are empty. I swear some users think gifters have telepathic powers or something…

It is a very common thing that someone put a key to a giveaway and the key is not valid for some reason. Mostly it is not done intentionally. Next time try to contact the creator and tell them about it. Mostly you get a new working key if you do it. It is a matter of politeness to write them.

was op suspended just for asking ?

op IS suspended

Como já falaram, antes de marcar como "not received" primeiro você deve falar com o criador do sorteio. É considerado extramente rude simplesmente marcar assim como vc fez. Bem, qql outra duvida eu sugiro ler o FAQ ou perguntar pra alguém. :)