Thanks for your payment, and for your extremely accurate description of your problem.
This is a side-effect of the change to 15% VAT. Your copy of the software knows nothing about it and would have printed an incorrect invoice showing 17.5% VAT. We didn't anticipate that VAT might change at such short notice and we hadn't considered what effect it might have on our "self-print" invoices.
Anyway, you can easily solve your problem simply by downloading the latest software from our website, installing it (your data will automatically be upgraded), and retrieving the licence again. Sorry for the inconvenience.