Tricky one

Hi all I hope someone can help me with this "glitch" please. I recently sold an item for which I sent an invoice with payment instructions to the buyer. Immediately after sending the invoice my listings showed another 2 items had been purchased by the same buyer, therefor I sent another invoice for these 2. The buyer contacted me to say that the items had not been purchased. There was then no record on my sales that the 2 items had actually been bought & they showed as still being listed as being auctioned. This has now confused me & the buyer (mainly re- invoices). The buyer wants to buy the 2 items previously mentioned but seems reluctant to action the invoices??

Thanks for any replies.