Are you trying to redeem your free copy of Amplitude for backing the kickstarter but having no success?
Harmonix have offered some advice on how to fix this. To begin with, they ask for you to search your spam and junk mail folders for an instructional email from: [email protected]
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.