Error when accessing workflow management - [Object reference not set to an instance of an object]

[harryr]

I recently upgraded the Nintex Workflow installation to 3.6.2.0 on our single server, on premise 2013 farm. Now when I select "Manage Workflows with Nintex Workflow" in the Library menu, I get an error that reads: 

[NullReferenceException: Object reference not set to an instance of an object.]
   Nintex.Workflow.ApplicationPages.WorkflowInventoryControl.Page_Load(Object sender, EventArgs e) +471
   System.Web.UI.Control.OnLoad(EventArgs e) +85
   System.Web.UI.Control.LoadRecursive() +128
   System.Web.UI.Control.LoadRecursive() +225
   System.Web.UI.Control.LoadRecursive() +225
   System.Web.UI.Control.LoadRecursive() +225
   System.Web.UI.Control.LoadRecursive() +225
   System.Web.UI.Control.LoadRecursive() +225
   System.Web.UI.Control.LoadRecursive() +225
   System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint) +3711

The workflows are still running but I can't access them. I rid upgrade the Nintex databases after installation as it produced a flag.

Can anyone form Nintex please help?

[redpanda]

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