Are you trying to redeem your free copy of Amplitude for backing the kickstarter but having no success?
If you are in Europe however there is a current issue with the console redemption process that is being looked into so you may have to hold off on playing Amplitude for a little while longer yet.
The countries currently being affected by the ‘invalid code’ issue are:
Australia, New Zealand, Austria, Belgium, Denmark, Finland, Luxembourg, Netherlands, Norway, Poland, Portugal, Spain, Sweden, and Switzerland.
If you are in North America you can contact Harmonix via their Kickstarter page for the game and they can assist you there also.