This is caused by an image which contains transparent layers. This is something Pay & Bill currently does not support and the invoice print process will crash your system.
Please contact us via the MyAccess portal and include the following details:
Article Title.
Version No (bottom right corner of Pay & Bill).
A screenshot of the error message.
Copy of the error log (click on copy details and paste contents into notepad).
Employer you are printing invoices for.
Screenshot of parameters used for failed invoice print.