Offline Activation C#

I'm using the TurboActive 4.0 API in a C# application and trying to get the offline activation process working.

When I call this method:ta.ActivationRequestToFile(saveFileDialog.FileName, Environment.UserName);

I get the following exception message:The product key is invalid or there's no product key.

So it looks like I need to call ta.CheckandSavePKey(String) before this.

But where do I get a product key from?

To add some more information, I am running under a verified trial which doesn't require a product key. So there is no product key to pass into the method.

Verified trials don't use product keys, and thus have a different separate API:

https://wyday.com/limelm/help/trials/#ut-veri-req