An element associated with the workflow cannot be found

Symptoms

When attempting to copy a workflow, Sharegate displays the following error message:

An element associated with the workflow cannot be found.

Error code

Details

Solution

1 - For system (out-of-the-box) workflows:
Go in SharePoint (in your browser) and navigate to the settings of the workflow causing problems. Make sure the selected Task List and History List (if applicable) are valid and save the workflow. Even if it seems valid, saving it will help since SharePoint will fix broken references when doing so, even if they don't show as broken in the user interface. 

2 - For Sharepoint 2007 workflows built with SharePoint Designer:
Open SharePoint Designer and connect to your source site. Find the problematic workflow and simply publish it (without changing anything). SharePoint Designer will correct the broken references and you should then be able to copy the workflow with Sharegate. 

3 - For Sharepoint 2010 and more recent versions workflows built with Sharepoint Designer:
Open Sharepoint Designer and connect to your source site. Find the problematic workflow and open it. In the Settings section, make sure that existing lists are selected in the Task List and History List fields. Publish the workflow. SharePoint Designer will correct the broken references and you should then be able to copy the workflow with Sharegate.

It is possible that SharePoint Designer will give you an error when trying to publish the workflow. This would mean that the workflow is currently invalid and that it needs to be fixed before Sharegate can copy it. Such a workflow can normally not be ran, so it is possible that it is simply a workflow that is no longer used and that can be safely ignored when migrating.