This just started popping up for me.  I didn't realize until I noticed I wasn't getting paid for any invoices.  Then I saw the alerts in the Sales / Invoice section.

This doesn't seem to be a bounced email issue, as no matter which email I put in the field, same error occurs. This is an issue with not being able to send out any invoices from QBO.  Can't resend, and only solution it offers to attempt to resend the invoice with the same error.

It is now Dec 2022 and issue is still not resolved.