I really appreciate all of those details, @PizzaPlus. Tracking Sales Reps can be tricky, and you've already verified a specific customer has assigned to it. I'm here to help show the transactions to the report and make sure you'll be an expert at it in no time.
You're right. You'll need to add the Reps per transaction to show them on the report. Not to worry, I'll share a way to do that.
Let's customize the sales order, purchase orders, and invoices template. I'll show you how:
- Go to Customers at the top, then click Customer Center.

- Under the Transactions, select the Invoices.
- Locate the customer's name.

- On that page, go to the Formatting tab and then Customize Data Layout.

- In the window that appears, select the Header tab.
- Find REP on the list and select the Screen and Print boxes to add it.
- Hit OK once done.

See this article for detailed guidance: Create and use custom fields in QuickBooks Desktop.
With all of that information, you should be on track to finish running Sales rep by transaction with ease. However, if you have any more questions about this, or other issues while learning QBDT, I am always here to assist in whatever way I can. In the meantime, I hope you have a great day.