This issue is caused by the Invoice Layout not being set in the Invoice Configuration File.
To check this, please follow the steps below:
Open the Customer Screen.
Click Invoices.
Click Invoice Configuration.
If the Invoice Layout field is blank, Edit the record and select the Correct Value from the Invoice Layout dropdown.
If the Use Account Invoice Configuration field is ticked, go back to the Customer Screen and Click the Account Link to take you to the Account screen.
Click Invoice Config (Alt + N) from the links on the right hand side.
Check the Invoice Layout field, Edit the record and select the Correct Value from the Invoice Layout dropdown.
Save any Changes.
Need further help?
If this still does not resolve the issue, please raise a support case, including the customer number, and we will make the required update
Please supply the customer number and invoice number when raising the case.