Nintex Workflow would not start automatically after publishing in SharePoint 2010

Issue:

The workflow was set to automatically start when a new item was created and an existing item was modified. After adding a new item the workflow did not start and when selected the item and clicked on the workflow button from the ribbion there was error message "user cannot be found". Checked the server event logs and the following message was recorded:

Error loading and running event receiver Microsoft.SharePoint.Workflow.SPWorkflowAutostartEventReceiver in Microsoft.SharePoint, Version=14.0.0.0, Culture=neutral, PublicKeyToken=71e9bce111e9429c. Additional information is below.

: User cannot be found.
Event ID: 6875


Debugging steps

I took over someone else and had to background knowledge as what had happened earlier. The current site was a SP 2010 site, with Nintex workflow 2010.

• I tried creating a test workflow and that failed to start as well
• created a test workflow in a different site collection and this worked fine, so the issue was with the current site collection

 Resolution:

I opened up SharePoint designer and clicked on wokflows, to my surprise I found that the out of the box user was set to a claims based format e.g. "0;#id", but the current web application was classic mode so I edited the workflow and saved it back (did not make any changes, just opened and saved) this updated the workflow with my current user id.

After which the workflows started working.

Hope this helps :)