If you have a secured environment that does not grant anonymous access to build artifacts then it is impossible to use copyArtifact in a workflow step even when setting the workflow to run as a user that has administration rights.

ERROR: Unable to find project for artifact copy: producer
This may be due to incorrect project name or permission settings; see help for project name in job configuration.

Attached is a Jenkins home with 2 jobs that demonstrates the issue.
the username is "admin" with password "admin" - *note* all plugins will need to be installed.