Error occurred. Unable to preview workflow.

Received the following error on the Workflow Progress screen when reviewing the history of a Nintex Workflow:

Error occurred. Unable to preview workflow.

I resolved this issue by deleting workflow actions that were disabled in the workflow.  The specific actions I deleted were the “Copy to SharePoint” and “Create new item” actions.  Once I deleted them and republished the workflow, I was able to preview the workflow on the Workflow Progress screen.