eBay do have a habit of shooting first and then asking questions later. Actually, that's incorrect, the shoot first and rarely ask any questions at all, as you've just discovered.
I have to admit, hard to imagine what has caused this reaction judging from what you wrote. I'm assuming this is a new account and perhaps this was your first listing?
If that is so, the only possible thing I can think of that would cause this type of reaction is that you listed a banned video game, but that will only usually result in the listing being removed, not account suspension, unless you do it again.
Can you fill us in on more details in regards to the listing. Is the account a new one, what was the game title, is it a new game, did you own it or were you drop shipping and so on.
Give as many details as possible and I'll see if I can identify a possible reason for you.
Now, in regards to getting your account reactivated. This is never an easy thing to do, but it starts with you having proof of of the products authenticity.
I've never heard of having to proof a video game is authentic before, but outside of that, I don't know what on earth the issue could be.
Anyway, drop us some details and I'll be better able to advise.