I'm here to ensure this gets investigated, @lledgersllc.

I understand how convenient it is to view the attached file to your invoices, and  I read all the responses and all the possible troubleshooting steps have already been shared to get this fix. I suggest reaching out to our QuickBooks Support Team to further investigate why you're unable to view the attached file to your invoices. They're also equipped with tools to determine the main cause of this.

Here's how to reach our support: 

1. Go to the Help menu, then choose Contact Us.
2. Type your concern in the box and hit Let's talk.
3. Choose either Get a call or Start a chat.
4. Complete the needed information, then submit the request.

Make sure to contact them within business hours to ensure a swift response.

For future reference, I'm also adding an article that can help you get paid faster with QuickBooks invoicing. It also helps you learn about how to let your customer pay their invoice securely, and easily track their payments.

Feel free to get back here should you have additional concerns about invoice attachments. We're always delighted to help.