Thanks for getting back to us, ShadyLady.
I appreciate your effort in performing some troubleshooting steps to resolve the issue. Allow me to take over and help you sort this out.
You may want to use terms on your invoices. QuickBooks will treat invoices as DUE UPON RECEIPT if you will not use TERMS in your invoices.
Here's an article with detailed steps and information about payment terms: https://quickbooks.intuit.com/community/Payments/Set-up-payment-terms/td-p/203687.
If you're still getting the same issue, let's try repairing your QuickBooks Desktop. Repairing QuickBooks can to fix program-related issues or errors.
I've got an article for your reference: https://quickbooks.intuit.com/community/Getting-Started/Fix-QuickBooks-Desktop-Windows/m-p/201490.
Please let me know how it goes or if you ran into a different situation by a reply below.