Error Loading Block: Registration Entry With Slots Show Details

F:\Rock\wwwroot\Plugins\com_bemaservices\CustomBlocks\BEMA\Event\RegistrationEntryWithSlots.ascx.cs(311): error CS0246: The type or namespace name 'DigitalSignatureComponent' could not be found (are you missing a using directive or an assembly reference?)

   at System.Web.Compilation.BuildManager.CompileWebFile(VirtualPath virtualPath)
   at System.Web.Compilation.BuildManager.GetVPathBuildResultInternal(VirtualPath virtualPath, Boolean noBuild, Boolean allowCrossApp, Boolean allowBuildInPrecompile, Boolean throwIfNotFound, Boolean ensureIsUpToDate)
   at System.Web.Compilation.BuildManager.GetVPathBuildResultWithNoAssert(HttpContext context, VirtualPath virtualPath, Boolean noBuild, Boolean allowCrossApp, Boolean allowBuildInPrecompile, Boolean throwIfNotFound, Boolean ensureIsUpToDate)
   at System.Web.Compilation.BuildManager.GetVPathBuildResult(HttpContext context, VirtualPath virtualPath, Boolean noBuild, Boolean allowCrossApp, Boolean allowBuildInPrecompile, Boolean ensureIsUpToDate)
   at System.Web.UI.TemplateControl.LoadControl(VirtualPath virtualPath)
   at Rock.Web.UI.RockPage.OnInit(EventArgs e) in \\Rock\Web\UI\RockPage.cs:line 1200