HP is a company that does not value its customers. It offers cash back deals for devices purchased which are nothing more than a scam. After trying to claim you realise that the so called Terms and Conditions are made to make it very difficult to actually claim the money back using any excuse to refuse to pay.
If you cannot afford to run a cash back scheme then don't offer one. As a long time HP customer I will NEVER be buying another HP product again nor recommending HP products to my friends and family nor purchasing anymore HP servers, desktops, printers or switches.
You can pat yourselves on the back for losing a long term customer and tens of thousands of pounds in sales. Well done good work, no wonder HP is in the mess its in.