Update Item Action Showing As Not Configured When Previewing Workflow Before Running the Workflow

Issue

When previewing a reusable workflow, the Update Item action does not appear to be configured, causing the workflow to fail.

Resolution

1. Open the reusable workflow causing issues in the Nintex Workflow designer by going to the SharePoint cog menu and selecting Nintex Workflow > Manage Reusable Workflow Templates. 
2. Click on Workflow Settings in the Nintex Workflow designer ribbon.
3. Click on Association Columns.
4. Delete any site columns added and recreate them.
5. Publish reusable workflow.