This happens from time to time and can be caused by the following.
1. A mistake in spelling your email address during checkout.
2. Logging in with a different email address than the one you used to make the purchase.
3. Setting up the password (after the checkout process) with a different email address than you used to make the purchase.
In addition Internet Explorer has been known to cause issues with our system. Try using Chrome or Firefox if possible.
Any of these items can cause this error. Please send us an email at firstname.lastname@example.org or by simply starting a trouble ticket to get this resolved.