Workflow Instance deleted without been cancelled

Whether you use SharePoint designer workflows or Nintex workflows?

If you use SharePoint designer workflows, you could try to use PowerShell to terminate a workflow instance.

Add-PSSnapin Microsoft.SharePoint.PowerShell -ErrorAction SilentlyContinue  
   
$web = Get-SPWeb "http://your-sharepoint-site-url"  
   
#Get the List  
$list = $web.Lists["Your-List-Name"]  
   
#Get the specific workflow, Associated with the list  
$WorkFlowToCancel = "your workflow name"  
   
# Iterate through all Items and all Workflows on Items  
foreach ($item in $list.Items)  
{  
   foreach ($wf in $item.Workflows)  
     {  
        #Check for the particular workflow  
        if( ($wf.ParentAssociation.Name -eq $WorkFlowToCancel) -and ($wf.IsCompleted -ne $true) -and($wf.StatusText -ne "Canceled"  ))  
        {  
            write-host "Previous workflow status:"  $wf.InternalState  
            #Cancel Workflow  
            [Microsoft.SharePoint.Workflow.SPWorkflowManager]::CancelWorkflow($wf)       
            write-host "Workflow Cancelled at $($list.title)! "  
        }  
     }  
}

If you use Nintex workflows, it is recommended that you contact Microsoft Customer Support Services (CSS) via telephone (a dedicated Support Professional can assist you in a more efficient manner) to confirm whether the Microsoft support team supports Nintex workflow issues.

Please go to the website to find related number and call it to create a new Phone Service Request to Microsoft Phone Support team. As remind, you might be charged for phone support service.

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