The error indicates form manager is needed on the template or page you are referring to. There is a control at this page that requires is, add the below markup to the template to load form manager and resolve the problem.
<%@ Register Assembly="Telerik.Sitefinity" Namespace="Telerik.Sitefinity.Web.UI.FieldControls" TagPrefix="sfFields" %>
<%@ Register Assembly="Telerik.Sitefinity" Namespace="Telerik.Sitefinity.Web.UI.Fields" TagPrefix="sfFields" %>
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