Problem
An email was sent to a customer but the link to pay the invoice was not included. The customer can't pay the invoice without the link.
Solution
The most common reason for a payment link to be missing from the emailed invoice is because the business unit is not set up for the payment processor.
Add business unit to the payment type
Go to the navigation bar and click Settings
.In the side panel, go to Integrations > Payment Processing.
Select the tab for the payment.

Look for the account you use and click Edit.
On the Online Payments Account screen that opens, select the business unit you want to include.

When finished, click Save.