When attempting to print after an upgrade, an invalid or unknown printer appears as the default. This issue happens most commonly right after an upgrade.
If you are attempting to print reports and an unknown printer appears as the default selection check Setup. If the default printer is correct in Setup but still appears as an invalid printer try the following:
Open the Sage Shared Data Directory (find this by going to Help -> System Settings)
Close Sage 300 ERP
Find the Users folder in the Shared Data Directory
Open the folder for the User having the issue
Find the file with the company name followed by _P.ism (e.g. SAMLTD_P.ism)
Rename the above file (e.g. SAMLTD_P.ism.old)
Launch Sage 300 ERP again
These steps should resolve the issue and have Sage selecting the correct default printer again. Note that this process will reset all printer settings to default.
Please also see these related articles: Printing to print boss printer does not print or email; Printboss forms are not printing or emailing; Print Boss error 'It is illogical for PrintBoss to print to itself" and Printing a large batch of documents using PrintBoss.