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: 

eNullReferenceException: 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?