I appreciate the update that you gave, @HAM9.
Allow me to provide additional insights to get this PDF invoice attachment issue sorted out.
To start with, let's try accessing the email that you've sent on a private window. At times, the stored data on the regular browser may lead to unusual behavior like the missing PDF attachment of the invoice.
If it works perfectly, you may clear the browsers' cache to remove the unnecessary data and refresh your files. It also prevents this hurdle from occurring.
However, if the problem continues after performing the steps above, I recommend contacting our Customer Care Team. They have the tools that can help conduct a further investigation in this matter to identify its root cause.
To add up, I'd like to share these resources below, which provides instructions when you encounter delivery errors due to attachments upon emailing sales forms in QBO, together with viewing the list of bounced emails:
I'll be right here to assist you if you have any other questions or concerns. Just leave a reply below. Take care!
