It's been several weeks now without a reply, can someone help with this? I'm paying for a product I can't use.

Prior to installing VM Invoice, the shopkeeper received an email with the order and 4 digits from the card number to allow them to complete the purchase, using the VM standard payment plugin for offline credit cards.
Since installing VM Invoice, they are not receiving any order notifications and the four digits are 'lost'.
Can you advise why this is happening?
Thanks