When an invoice has multiple rows, enter the same invoice number in every row that's part of that invoice.

I just upgraded to QuickBooks Online Advanced. I'm trying to use the Invoice Import feature, but I keep receiving the below.

I'm testing my first file, and I get this error in every situation.  I will not have invoice numbers on my imports and I will have multiple line items per customer. What is strange is that I get this error even if the .csv file only has one line item. I have tried with a single line and with multiple lines, I've tried with "Custom transaction numbers" turned off and on as instructed in this Importing invoices in bulk How-To article. Can anyone tell what I'm doing wrong? Here's what my .csv file looks like (customer name changed for privacy).

Thanks for your help!