Can you see all workflow and how many running ?

Issue is that you may stop all running but this is not what you wish. 

Drop an email to support because it sounds like an orphan running instance of a workflow. They may see more logs and help to kill it. 

Open site with SharePoint designer and it may still be listed in the workflows section.

I've had may issues with this type of thing, one time I had to delete the whole site to clean it all up.

Have you found a solution in the meanwhile?

Can you tell us how you where able to fix this issue

Regards

Oliver

I have been unable to work on this or any other Nintex item as their 365 solution is completely broken on my site collection.  Neither Nintex Support nor Microsoft support has been able to resolve the issue in over three weeks...

Sad to hear that.

Do you have a Plan B, if there will not find any solution, like to build a new SiteCollection and copy the data from the old one?

Regards

Oliver

If Nintex has such broken software that it will not run then they will be fired and replaced by a vendor with working software.

Sounds like a SharePoint / office 365 issue if you can't even see workflows in SPD so any workflow solution will fail too, unless using their own platform like some competitor but they different architecture. 

Still recommend to do the same on a different site collection and it will work. 

‌ we have the same issue with our Nintex subscription.  Microsoft support can't help and Nintex won't respond to cases regarding this issue (see attached image)

. 

Nintex O365 subscription overview shows we have 20 workflows.  13 of those are orphaned workflows that have no way to be deleted.  Only 7 are valid workflows.  We are working to replace ALL Nintex workflows with Microsoft Flow or Logic Apps.  

Yes - I moved to Flow due to the customer service issues.  However - in my case - the issue deleting the workflow was the result of a retention policy on my site.  I had to remove the O365 retention policy then I could delete the workflow.  Afterwards I re-applied the retention policy.   Nintex should have been able to 1. Been interested in helping a customer and 2. Been able to find that solution.

My feeling is the entire reason Microsoft developed Flow was because of all the complaints they get about Nintex.