Update: IG Victora II keys are not working. Dont create a giveaway.

Without more information, I can't say for sure. Maybe you purchased A House Divided, which is an expansion.
In any case, check in with IG support. They don't bite (and are, in fact, quite friendly)
Edit: Is it the one that was just unlocked from the Magicka bundle?

Please first activate the original game

The product code you've entered requires ownership of another product before activation.

If you are trying to activate an expansion pack or downloadable content, please first activate the original game, then activate this additional content.

I get the same thing , can't activate the key.

same for me

Same here, can't activate it either.

The key is for A House Divided, just activated it.

They removed it from Indie Gala.

Aye, it seems they accidentally gave out keys for the expansion.
And that they've removed it to fix the issue.

Generic Email Response:

Dear.

It was a problem, very sorry about it.

We are working with the publisher to find a solution ( have also the original victoria or another game )
we 'll let you know soon. Stay tuned.

Apologies.

Damn it's a shame I missed this. Been waiting for a chance to pick up the keys cheap for ages. Anyone know if they plan to bring back the expansion or just the base game?