G2A.com are allowed to sell the key to Steam?

So I'm allowed? Why I bought a CD Key Thief, but when I activate it on Steam tells me "Duplicate CD Key" and these G2A.com they said "Hi

Please contact Steam Support about the issue and Provide me with screenshot of activation of the key dates That They provide.

regards

Daniel "

Luckily I gave only 8 Euros and no more.

They are an unauthorised reseller. That means that the keys should be legit but Steam won't provide support for them. That said, Steam won't normally provide support for resellers, the reseller should be supporting themselves. Provide what G2A are asking for and they should provide you with a working key, they've clearly screwed up. Don't bother contacting Steam support, they can't/won't help.

Read this. G2A isn't a trustworthy seller.

When you buy from users in g2a, you can use the g2a shield, if the key is already used you should get your money back.

I had only positive experience with them.

No they are not. They're unauthorized resellers. There's no difference between buying from them and buying from a random guy in an alley or on Ebay, except Ebay doesn't allow codes/cd-keys to be sold.

authorised reseller or not g2a is 100% legit. I never had problem with them. You need to be carefull when buying from community sellers, use the shield if you want to be 100% sure.
p.s. paypal is a partner with g2a.com they ofen make offers.
p.s.2 g2a.com makes quite huge donations (save the childrens etc)