Hi @gpllc,

Thank you for your reply. 

If that's the case, I suggest you go through the steps in the article shared by my colleague @MarsStephanieL above. In case you missed it, I'll share with you the first set of steps.

Here's how:

1. Close QuickBooks Desktop (QBDT).
2. Open the Windows Start menu.
3. Search for QuickBooks. Then right-click the QuickBooks icon and select Open file location.
4. In the folder, right-click the QuickBooks.exe file and select Properties.
5. Select the Compatibility tab.
6. Select to uncheck the Run this program as Administrator option. If the option is grayed out, select Show Settings for All Users. This makes the option available.
7. Select Apply and then OK.

At this point, you can open your QBDT company and send a test email to see if it works. If the issue persists, refer to this article: How to fix "Error: QuickBooks is unable to send your email to Outlook". Scroll down and look for Step 2: Edit your email preferences in QuickBooks.

Once you have this taken care of, see this article: Verify that an invoice was emailed and read by recipient. It has the steps you can follow to track your invoice status. See if you have sent it and if your customer already viewed it. 

Post a reply if you have other questions sending invoices in QBDT, and I'll get back to you.