I went to the first item and clicked on Send Invoice.

The Invoice then came up with both items and doubled the postage.  I just changed the postage and sent the Invoice.

Yes, that's how it usually works for me too. Just not recently, at least not always.

If the buyer, for example, doesn't realize they bought two items from the same seller, eBay will nevertheless combine them (as well as summing the postage) when they try to pay for the first one. eBay actually says it will do this - that it combines items bought less than 3 days apart - but sometimes it just doesn't work.