Why can't I send a combined invoice?

HI



I have a buyer who purchased an item 4 days ago and I sent the initial invoice.  They then won a 2 more items today and when I go in to send a new invoice, it only shows the 2 new ones?  I've tried to go into the initial invoice and resend - but it has not added the other 2 purchases?  Can someone please help please 😛



Thanks!