"Unknown Error During Publish"
This is a generic error and you will see this message on this blog with multiple solutions.
In this scenario, the reason for the error was discovered after using standard Troubleshooting steps. The Job was a DWF created on a specific file. Regardless of which Job Processor client was used the DWF file persistently failed to generated.
Opening the ipt file in Inventor was successful, but when trying to publish the DWF manually (Export>DWF), a message appeared.
"Excel installation is required for this operation. Failed to launch Excel."
The file was an iPart and Excel was not installed on any of the Job Processor clients.