Brand approval denied

Hi all I`m tearing my hair out here, I have purchased twenty items from a brand manufacturer, I have an invoice, showing brand details, my details, the amount of units purchased, I have tried uploading this invoice for approval to sell more than six times and every time I get the automated response "We cannot accept this Invoice because we are unable to verify the transaction with the supplier. Documents must be authentic and unaltered in order to be verified." Does anyone have any ideas how I can rectify this issue, I dont see how I can give Amazon any more than theyre asking for??

Thanks in advance