This article provides a solution for the error: The record in table Print Request already exist. Identification fields and values: No. ='xx'
This could happen to any report, in this case it came on the Sales Invoice report.
How to solve it:
Please go into the Lasernet - Setup - Report Template Codes.
In here you will find duplicate records and that is causing the error.
To remove the duplicates, please select the Reset Templates button from the top menu.
This will remove all duplicates and you are now able to print again with the error message.