Hey there, @AMParsons. Thank you for reaching out to the Community.

I understand the urgency of attaching files to invoices and sending them to customers through QuickBooks Online.

At the moment, there's an ongoing investigation related to undelivered invoices. Rest assured, our product engineers are working to determine the reason to provide a resolution. I recommend contacting our phone or chat support to include you in the list of affected users. Just provide your name, updated email address, and the investigation number, INV-93532, to be notified via email.

In the meantime, I suggest manually sending the invoice to your customer outside of QuickBooks.

Once the case is resolved, you can record invoice payments to balance your accounts.

Please feel free to reach out if you have any follow-up concerns regarding invoices. It would be my pleasure to assist you. Have a good one!