Issue
When running a workflow with a Flexi task assigned to a workflow variable containing a SharePoint group, the following error might occur:
Error in task. User cannot be found.
An error has occurred in <workflow name>
Error in task. User cannot be found.
An error has occurred in <workflow name>
Resolution
This is a known Defect that was was addressed in Nintex Workflow for SharePoint 2013 version 3.2.5.0.
Error Code
Error in task. User cannot be found.
Related Links
Nintex Workflow 2013 Release Notes
https://community.nintex.com/t5/Release-Notes/Nintex-Workflow-2013-Release-Notes/ta-p/87903
Product Update Process
https://community.nintex.com/t5/Nintex-for-SharePoint/Nintex-Workflow-2013-Product-Update-Process/td-p/83881
Product Update - What you need to know
https://community.nintex.com/t5/Nintex-for-SharePoint/Updating-Nintex-for-SharePoint-What-you-need-to-know/td-p/86581
https://community.nintex.com/t5/Release-Notes/Nintex-Workflow-2013-Release-Notes/ta-p/87903
Product Update Process
https://community.nintex.com/t5/Nintex-for-SharePoint/Nintex-Workflow-2013-Product-Update-Process/td-p/83881
Product Update - What you need to know
https://community.nintex.com/t5/Nintex-for-SharePoint/Updating-Nintex-for-SharePoint-What-you-need-to-know/td-p/86581