Greetings, @mlovely. 

Thanks for joining in on this thread. I can see how beneficial sending invoices and attachments from your QuickBooks Desktop (QBDT) account would be for your business. However, I do recommend contacting our Customer Support Team again. They can use a screen share to help walk you through some more steps to help resolve this problem. 

Here's how: 

1. Go to the Help menu. 
2. Select the QuickBooks Desktop Help option. 
3. Press the Contact Us hyperlink. 
4. Type in your question and tap Continue. 
5. Scroll down and choose to Get a Callback. 

That's all there is to it. For future reference, you can check out our QuickBooks Blog to see what's new in the product. 

This will be the best way to get your issue resolved as soon as possible. Should you need any further information, please don't hesitate to contact me. Have a great day!