This error usually occurs when the the computer can't access the printer due to changes in the printer driver or network. The error can also be caused by a corrupt picture in the template.
Start by creating a new printer binding, you can see how here
If you can print other templates or products the error might be caused by a corrupt picture. Perform the following steps:
Exit Shoppa
Open the Windows start menu and type %appdata% and press Enter
Open the “Shoppa” folder within %appdata%
Find the folder with the name “cache”
Delete the cache folder
Start Shoppa
This process should result in Shoppa downloading a new picture when printing which should resolve the issue.