Free Castle Link

Hey guys I have a little problem. I bought my Mamba Max Pro a few months ago and when I tried to use the code that it came with to get a castle link it said it was an invalid code. Sense then I moved and I lost the little paper with the code on it , is there any way I can still get a free castle link? I have proof of purchase can I just shoot Castle an e-mail, or do I just need to buy one? Thanks for the help!

EDIT: I should have looked again before I posted... I just found it mixed in with a bunch of my receipts. Please delete this, or lock it.