Hi there, paodesigns.
We recently received a report about the Undeliverable error when sending an invoice to a customer. Our product team is working diligently, and an open investigation is taking place to resolve the problem.
At this time, you can download the invoice and email from their emails rather than through QBO as a workaround.
I suggest contacting our QuickBooks Support Team, so they can add you to our notification list. This will help our engineers determine the number of affected users. You'll also receive an update through email once this has been resolved.
- Open your QuickBooks Account.
- At the top right, click the Help icon.
- Type Resubscribe in the Type something field.
- Click I still need a human.
- Hit Contact us.
- You'll be routed into the How can we hep? page. Then, select how you want to contact them and fill in the information.
You can browse this article to learn more about the different types of support we offer at Intuit and its availability: Support hours and types.
Please refer to this article to see steps on how you can group multiple payments together into a single record for an invoice: Record invoice payments in QuickBooks Online.
Let me know if there's anything else you need help with. Know that I'm always here to help you anytime. Take care and keep safe!