_Problem_

Weeks? Why are you wait for so long? Can you choose a new winner?

they got a week to claim, after that you put in a ticket and ask for a re roll.

From FAQ:

What should I do if the winner of my giveaway has not redeemed their gift, and I'm unable to get into contact with them?
If you contacted the winner of your giveaway on email and Steam over one week ago and they have not yet responded or redeemed any keys or gifts you attempted to send, please contact support to request a new winner. When creating a ticket, we ask you to include data that suggests you made an adequate attempt to contact the winner, such as screenshots of emails, friend requests, or gifts pending on Steam. If the request is approved, a new winner will be generated by the site.

7 days. After that ask for a re-roll.

Once the seven-day grace period has expired, you should do two things:

1) Toggle the key "off" so it can no longer be viewed.
2) File a support ticket for a re-roll.

If the key has not yet been viewed, it should be an easy matter to re-roll it. In those cases where the key was viewed but the winner is unresponsive, things get a bit tricky.