Thank you for bringing this to our attention, cbruceuss.

You should be able to add an attachment to your invoices from the Attachments section. If not, I recommend adding up the file using a private window. In most cases, unexpected behavior while working with QuickBooks is caused by too much cache stock on the regular browser you're using.

To save you time, use either of these keyboard shortcuts:

• Google Chrome: Ctrl + Shift + N
• Safari 11 or newer: ⌘ + Shift + N
• Mozilla Firefox: Ctrl + Shift + P
• Microsoft Edge: Ctrl + Shift + P

If it works, I recommend going back to your original browser, then clear its cache to start fresh. You can also use other supported browsers and have added Intuit as a trusted site to prevent your browser from potentially blocking site content.

You can read this article to learn more about attachments: Attachments in QuickBooks Online.

If the same thing happens, I recommend contacting our Support team. That way, they can start a screen-sharing session to properly document this case. I know attachments are very important, and with your help, our team can gather a lot of data to identify the root cause of this behavior and prevent further issues. 

As always, feel free to visit our QuickBooks Community help website if you need tips and related articles in the future.

Please know you can continue to reach me here with any additional questions. Thanks for coming to the Community, wishing you continued success.