I appreciate you for performing the steps to resolve the issue, TOcondonews.

I've checked here on my end and found that there is an investigation (INV-38793) about being unable to send invoices via email. I recommend contacting our QuickBooks Support Team, so you'll be added to the list of affected users. You can have the full contact information by going to the Help menu of the desktop company file. Then, you'll get real-time assistance via the Start a Message option.

Here are the complete steps:

1. From the Help menu, select QuickBooks Desktop Help.
2. In the Have a Question window, scroll down to click the Contact us link.
3. This will display the Contact Us screen.
4. Go to the Tell us more about your question section to enter INV-38793 in the field box.
5. Click the Search button to display the Start a Message button.

To ensure that you'll be assisted on time, please check out our support hours before performing the steps.

Let me share this article in case you want to learn more about managing sales and customer-related transactions in QuickBooks: Sales and Customers Help Articles.

Thank you for your patience while we're working on this. We got your back if there's anything else you need.