Sending multiple invoices to the same buyer

[michaepasciut-0]

I'm new to eBay so I'm a little lost and I need help. I had someone win 86 auctions of mine and I'm trying to send him invoices. Now I know eBay only puts 40 items per invoice which i understand that multiple need to be sent. Here's my problem... I sent one successfully and the buyer confirmed that he got it. When I go to send the second one it tells me it was successfully sent to buyer BUT (a) he never got it and (b) under "My eBay" it still asks me to send invoice. I've refreshed the page, signed in and out and even used a different computer to try it. Nothing has worked. I don't know what to do at this point. Suggestions?