It's important to send invoices on time, @weichin1. I know another way how to resolve undeliverable invoices in QuickBooks Online.
In addition to the steps you accomplished, I advise verifying the accuracy of the customers' email addresses. If those are correct and still they haven't received the invoice, let them check their junk or spam folders. This could be the root of the problem. After that, you can resend the invoices. Here's how:
- Click on Customer & leads, then hit Customers.
- Pick the customer who didn’t receive the invoice.
- Click on Edit.
- Confirm the email address and edit it if needed.
- Resend the invoice.
Your email address can also be checked in QBO. See this for the detailed steps: Troubleshoot if customers aren't receiving emails from QuickBooks Online.
I've also added this extra module about bounced emails: How to view a list of bounced emails with delivery errors.
Also check this if you want to personalize invoices or other sales forms in QBO: Customize invoices, estimates, and sales receipts in QuickBooks Online.
I'll make sure to respond as soon as I can. Just keep in touch if you need more help with invoices or QuickBooks. Stay safe.
