Error "Nintex Workflow 2013 is not activated for this Web Application"

ISSUE

When publishing a workflow, the following error occurs.
 

RESOLUTION

1. Navigate to Central Admin
2. Navigate to Nintex Workflow 
3. Select Web application activation 
4. Select the drop down and choose your Web application
5. Select the Checkbox "activate all web applications" (this will be for the site selected from the drop down)
6. Click OK
7. Go back to the site, reload the designer and republish the workflow.