Error when adding a Feature Map

I installed the latest Geocortext Essentials on our Amazon cloud servers. Everything seems to be working fine except when I try to add a feature map to a layer. I get the following message. Any help on this will be much appreciated.

Object reference not set to an instance of an object.

Controller: FeatureMaps

 

Action:

 

  Create

 

Error Info

 

Source: Geocortex.Essentials.RestManager

 

Message: Object reference not set to an instance of an object.

StackTrace: at Geocortex.Essentials.RestManager.Html.MapImageExtensions.FeatureMapImage(HtmlHelper helper, FeatureLayer featureLayer, FeatureMapDefinition featureMap, Int32 width, Int32 height, String altText)

 

   at ASP.views_featuremaps_edit_ascx.__Render__control1(HtmlTextWriter __w, Control parameterContainer)

 

   at System.Web.UI.Control.RenderChildrenInternal(HtmlTextWriter writer, ICollection children)

 

   at System.Web.UI.Control.RenderChildrenInternal(HtmlTextWriter writer, ICollection children)

 

   at System.Web.Mvc.ViewPage.Render(HtmlTextWriter writer)

 

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

 

Thanks in advance,

Sedat