Steam Re-Downloading Activation Code Problem

When attempting to re-download/play a game that requires a Steam account
and activation code
we are being told the activation code we used the original time
is no longer valid as it has already been used.
I there a way around this problem.

G'son is attempting to re-load/play Empire Total War Gold Edition,
and is at this moment quite frustrated.

Have you contacted Steam to ask for their help? Sometimes they are not very responsive, but it's up to them to allow you to re-download a game.

Will try, thanks!