Hi Brian, Sorry to hear of your problems registering Crazytalk 6.
When you say registration has failed, do you mean your serial number is not being accepted?
If this is the case then it may be that you are mixing up some letters which is very easy to do with certain serial numbers. The best way would be to copy and paste the serial number from your purchase email and see if this does the trick.
If after ensuring you have entered it correctly you can still not register it, then please get back to support and explain that your serial number is being rejected and that you purchased the software through Renderosity. They should be able to help you register it manually or explain the reasons why it can't be registered.