have you seen this documant ?

Yes.  But they address that error when coming from an email link.  I get the error consistently when using certain approval commands in the workflow, not otherwise.  Basically if I use a "request approval" I get this error in this workflow. 

could you post screenshot of your workflow and configuration of task action?

do you try to terminate task within workflow?

or do you have any other workflow that could close it in parallel?

could you post notification configuration as well?

if there some links within the mail, could you post an example how does link resolves at runtime?

I assume workflow errors out just after user responds to the task...

does the error happen with regular or Lazy approval? (btw, you do not have allowed lazy approval but perform some 'Lazy approval?' check, can you explain the contradiction?

does the error happen for both outcomes?

is there single approver behind PM_Email or may there be several approvers?

The workflow errors out before the user responds to the task, in fact even before sending out any notifications to the approver.
 

so does your workflow fail when it reaches request approval action? or does it fail on an other action/

do you get task notification at all?

could you check workflow task list whether there is created respective task item in case workflow fails?

It fails when it reaches the request approval action.  There is no notification.  The last task does create a log entry.

then it looks like it's a problem ever to create the task.

have you checked workflow task list as I advised?

I would suggest to carefully check whether user that runs the workflow has sufficient permissions on workflow task list.

or try to run workflow with a user which has given sufficient permissions.

Hi paul moscatt‌

I faced the same issue in my environment in May of this year. I was on  SP2010 and NW2010 then. The workflow never created the task and was showing this error as soon as it reached the Request Approval action. I ran the same workflow again and again on the same item and 4th or 5th time it would work and go through.

I engaged Nintex support as well but they couldn't help much as they kept saying that task should have been created. But it did not.

I ended up doing some cleaning on my end like nintex history list and looking at the Support Portal to find if there are any workflows that have errors.

Add a delay before your approval action.

If you check your logs, you might see something like this:

06/03/2016 15:15:03.84   OWSTIMER.EXE (0x1178)                            0x2470  SharePoint Foundation                    Workflow Infrastructure                      98d4       Unexpected         Nintex.Workflow.NWHumanApprovalException: Cannot find a corresponding human workflow task id for this task.     at Nintex.Workflow.HumanApproval.NintexTask.Jh4=(SPWeb Jx4=, Guid KB4=, Int32 KR4=)     at Nintex.Workflow.Activities.ApprovalActivityInternal2.ChildCompleted(Object sender, ReplicatorChildEventArgs e)     at System.Workflow.ComponentModel.Activity.RaiseGenericEvent(DependencyProperty dependencyEvent, Object sender, T e)     at System.Workflow.Activities.ReplicatorActivity.HandleStatusChange(ActivityExecutionContext executionContext, ActivityExecutionStatusChangedEventArgs e, ReplicatorSubscriber subscriber)     at System.Workflow.ComponentModel.ActivityExecutorDelegateInfo`1.ActivityExecutorDelegateOperation.Run(IWorkflowCoreRuntime workflowCoreRuntime)     at System.Workflow...     05fb1339-2159-4c44-bdf7-0f4989186403

06/03/2016 15:15:03.84* OWSTIMER.EXE (0x1178)                            0x2470  SharePoint Foundation                    Workflow Infrastructure                      98d4       Unexpected         ....Runtime.Scheduler.Run()          05fb1339-2159-4c44-bdf7-0f4989186403

So, to summarize, you may have to look at your logs and clean up the old history to free up some space.

I cannot tell for sure what resolved it but there are certainly other reasons than the ones documented.

Permissions look good.  I get this error just before the human taskflow error in ULS logs:

Error in CancellingParallelActivity.: System.InvalidOperationException: Could not find service of type 'Nintex.Workflow.Activities.Services.IReadWriteWorkflowVariables' through the currently configured services. Consider adding the service to ExternalDataExchangeService.     at System.Workflow.Activities.CallExternalMethodActivity.Execute(ActivityExecutionContext executionContext)     at System.Workflow.ComponentModel.ActivityExecutor`1.Execute(T activity, ActivityExecutionContext executionContext)     at System.Workflow.ComponentModel.ActivityExecutor`1.Execute(Activity activity, ActivityExecutionContext executionContext)     at System.Workflow.ComponentModel.ActivityExecutorOperation.Run(IWorkflowCoreRuntime workflowCoreRuntime)     at System.Workflow.Runtime.Scheduler.Run() (Build:2490)

I get this error in ULS logs just before the human task error:

Error in CancellingParallelActivity.: System.InvalidOperationException: Could not find service of type 'Nintex.Workflow.Activities.Services.IReadWriteWorkflowVariables' through the currently configured services. Consider adding the service to ExternalDataExchangeService.     at System.Workflow.Activities.CallExternalMethodActivity.Execute(ActivityExecutionContext executionContext)     at System.Workflow.ComponentModel.ActivityExecutor`1.Execute(T activity, ActivityExecutionContext executionContext)     at System.Workflow.ComponentModel.ActivityExecutor`1.Execute(Activity activity, ActivityExecutionContext executionContext)     at System.Workflow.ComponentModel.ActivityExecutorOperation.Run(IWorkflowCoreRuntime workflowCoreRuntime)     at System.Workflow.Runtime.Scheduler.Run() (Build:2490)

sounds like installation or configuration issue.

unfortunately I'm not able to say what exactly that might be.

I've been looking at the rebuild indexes bit suggested in this post Demystifying Workflow History (Part 2) | Nintex Community Some of my HumanWorkflow tables indexes are at like 80%+ fragmentation.

Did you resolve this ‌?

I have the same issue, has anyone found the root cause and how to resolve it..??
With mine though (for background) I have never been able to create tasks even with out of the box SharePoint Workflows, it sends a mail but doesn't create a task, I have always been told that this is due to our Exchange being 2010 while SharePoint is 2016... I have had consultants from 2 different companies have a look but they were never very interested in looking further into it after hearing that we're on Exchange 2010. Up until now we've used K2 for larger workflows and tasks but we are moving over to Nintex so I really need to get to the bottom of this problem.

If you have Nintex and it works, you have support. Just email support@nintex.com and they will create a ticket. It might take 24 hours for them to get back to you.

I did create some SQL server maintenance jobs to rebuild my indexes and I think that made a bit of difference (See my post above). In my farm these tables are pretty small so I don't think the indexes really matter.

I haven't had this issue in a long time, so it must have got fixed with the help of Nintex support.