Server Error in '/' Applicatio when activating "Nintex Forms" web app feature.

[#1]

Hi

I'm working on migration process. On of the machine I tried touninstall "Nintex Forms" according to document: NF2013_uninstall_guide.pdf.

One of the step is $farm.RemoveObsoleteClass("4DB6F71E-05FF-4383-B16E-ABC5A57057C5")

When I installed Nintex Forms again,

I can't add license, because I got message that "Nintex Forms has not been activated yet. Please go to Central Administration and activate the Nintex Forms under Web Application > Manage web application > Manage Features

I'm getting this error (bellow) when I try to enable "Nintex Forms" on my web application.

How can I solve this problem?

Error in the application.

Description:An unhandled exception occurred during
the execution of the current web request. Please review the stack trace for
more information about the error and where it originated in the code.


Exception Details: Nintex.Forms.SharePoint.Exceptions.NintexFormsNotActivatedException:
Error in the application.


Source Error:

An unhandled exception was generated
  during the execution of the current web request. Information regarding the
  origin and location of the exception can be identified using the exception
  stack trace below.

Stack Trace:

[NintexFormsNotActivatedException:
  Error in the application.]

 
  Nintex.Forms.SharePoint.Licensing.LicenseHelper.ReadLicenseFileFromDatabase()
  +591

[NintexFormsNotActivatedException:
  Error in the application.]

   Nintex.Forms.SharePoint.Licensing.LicenseHelper.ReadLicenseFileFromDatabase()
  +790

 
  Nintex.Forms.SharePoint.Licensing.LicenseHelper.ReadandCheckIfLicenseValidForFeatureActivation()
  +43

[SPException: Error in the
  application.]

   Nintex.Forms.SharePoint.Licensing.LicenseHelper.ReadandCheckIfLicenseValidForFeatureActivation()
  +479

 
  Nintex.Forms.SharePoint.EventReceivers.WebApplicationFeatureEventReceiver.FeatureActivated(SPFeatureReceiverProperties
  properties) +856

   Microsoft.SharePoint.SPFeature.DoActivationCallout(Boolean
  fActivate, Boolean fForce) +1730

 
  Microsoft.SharePoint.SPFeature.Activate(SPSite siteParent, SPWeb webParent,
  SPFeaturePropertyCollection props, SPFeatureActivateFlags activateFlags,
  Boolean fForce) +2949

 
  Microsoft.SharePoint.SPAdminFeatureCollection.Add(Guid featid,
  SPFeatureDefinition featdef, Version version, SPFeaturePropertyCollection
  props, Boolean fForce) +2361

 
  Microsoft.SharePoint.SPFeatureCollection.AddInternal(SPFeatureDefinition
  featdef, Version version, SPFeaturePropertyCollection properties,
  SPFeatureActivateFlags activateFlags, Boolean force, Boolean fMarkOnly) +779

 
  Microsoft.SharePoint.SPFeatureCollection.AddInternalWithName(Guid featureId,
  Int32 compatibilityLevel, String featureName, Version version,
  SPFeaturePropertyCollection properties, SPFeatureActivateFlags activateFlags,
  Boolean force, Boolean fMarkOnly, Boolean fIgnoreMissing,
  SPFeatureDefinitionScope featdefScope) +207

 
  Microsoft.SharePoint.WebControls.FeatureActivator.ActivateFeature(Guid
  featid, Int32 compatibilityLevel, SPFeatureDefinitionScope featdefScope) +1228

 
  Microsoft.SharePoint.WebControls.FeatureActivatorItem.ToggleFeatureActivation()
  +229

 
  System.Web.UI.WebControls.Button.RaisePostBackEvent(String eventArgument) +146

 
  System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint,
  Boolean includeStagesAfterAsyncPoint) +3586

---

Version
Information: Microsoft .NET Framework Version:4.0.30319; ASP.NET
Version:4.0.30319.18408

*******************************************************************************************

[#2]

Apparently "INSTALL-NFService" need to be run in SharePoint powershell to fix this problem.