I've downloaded the php library for amazon flexible payments. I am following the included instructions and ran CBUISingleUsePipelineSample.php, as the docs say. The instructions say "The return URL will include expiry, tokenID, status, callerReference and signature parameters."
When I run that file, expiry & tokenID are missing from my return URL & it says that callerReference is not well formed. I've followed the docs as it says. Where am I going wrong?