Hi there, The Lab.

I want to make sure your customers are receiving their invoices. Your customers may need to perform some steps as well.

Their email providers may have blocked our address. You can ask your customer to configure their server. 

I'm adding this article as your guide: 3 solutions for you when customers aren't receiving your emails. Then, follow Solution 3.

If the same issue persists, I recommend contacting our QuickBooks Live Team. That way, they'll be able to trace affected customers.

Don't hesitate to post again if there's anything else you need about customers not receiving invoices. I'll be right here to help you.