It's generally better to start a new discussion @connecticutskier since older ones are often connected to different issues.
eBay made some changes on June 23 that are preventing invoices in certain situations. Here's what they had to say about it:
The items sellers are reporting are considered "Autopay" which prevents an invoice being sent.
Autopay would be considered something like Immediate payment being required in listings. So for auctions, that would come into play if the seller used the 'Require immediate payment when buyer uses the Buy It Now' feature. It sounds like they are looking to find a way to improve the member experience though, so that's good to see.
A quick call out I want to make if sellers aren't requiring immediate payment, is to double check their shipping preferences to ensure they've checked the box to, "Allow buyers to send one combined payment for all items purchased."
The option to allow buyers to combine payments is a setting on this page. If you select anything longer than 3 days it can affect any automatic unpaid item settings you have in place on this page.
