Sitecore

Sitecore Error Troubleshooting: Experience Editor and Preview mode error in the sitecore CMS ribbon(Upgrade from sitecore 10.1 to 10.4)  -  Error Message ====================================================== 2080 07:28:08 ERROR Application error. Exception: System.Web.HttpUnhandledException Message: An unhandled exception occurred. Source: Sitecore.Mvc    at Sitecore.Mvc.Pipelines.MvcEvents.Exception.ShowAspNetErrorMessage.ShowErrorMessage(ExceptionContext exceptionContext, ExceptionArgs args)    at Sitecore.Mvc.Pipelines.MvcEvents.Exception.ShowAspNetErrorMessage.Process(ExceptionArgs args)    at (Object , Object )    at Sitecore.Pipelines.CorePipeline.Run(PipelineArgs args)    at Sitecore.Pipelines.DefaultCorePipelineManager.Run(String pipelineName, PipelineArgs args, String pipelineDomain, Boolean failIfNotExists)    at Sitecore.Pipelines.DefaultCorePipelineManager.Run(String pipelineName, PipelineArgs args, Strin...