Hi there, accounting191. 

I understand how important it is to deliver those sales forms to your customers. Let's see to it that this is addressed so you may resume your work.

I recommend contacting our Support Team so they'll be able to check the issue and, if necessary, alert our engineers.

To reach them:

1. Log in to your QuickBooks Online company.
2. Go Help (?).
3. In QB Assistant, enter a brief description of your issue or ask a question.
4. Click on Contact Us.
5. Choose a way to connect with them:

• Start a chat with a live support.
• Call  M-F, 8:00 AM to 10:00 PM and S-S, 8:00 AM to 6:00 PM.

I'm also adding these articles to guide you on how to troubleshoot email delivery issues. Although they are from another region, the UK version can also use the solutions:

• How to view list of bounced emails with delivery errors
• Delivery Errors when trying to email a sales form

Please let us know how it goes or if you still have other questions about undelivered sales forms. We'll be here to help you out. Have a great weekend!