Message: Cannot create unknown type '{http://schemas.uipath.com/workflow/activities}SendMail'

Help
#1

I have been using same WorkFlow many Times. But when I ran same flow through Command Line - the I got exception.
Message: Cannot create unknown type ‘{http://schemas.uipath.com/workflow/activities}SendMail’.

But now it is sending me same message when I am running using Studio.
Included all the Outlook packages.

#2

@atulgupta5
try to update or reinstall the mail package

#3

Exactly, do as @Sreelatha278 or try to downgrade the package, let us know what works best for you.

#4

Resolved this but now showing new issue:

Workflow Designer Encountered problem with your document

System.NullReferenceException: Object reference not set to an instance of an object.
at System.Activities.Debugger.XamlDebuggerXmlReader.InjectLineInfoMembersToBuffer(DocumentLocation startPosition, DocumentLocation endPosition)
at System.Activities.Debugger.XamlDebuggerXmlReader.InjectLineInfoXamlNodesToBuffer()
at System.Activities.Debugger.XamlDebuggerXmlReader.Read()
at System.Activities.XamlIntegration.DynamicActivityXamlReader.Read()
at Microsoft.Activities.Presentation.Xaml.ActivityTemplateFactoryBuilderReader.Read()
at Microsoft.Activities.Presentation.Xaml.ViewStateXamlHelper.StripViewStateElement(XamlReader inputReader, Dictionary2& viewStateInfo, Dictionary2& viewStateSourceLocationMap)
at Microsoft.Activities.Presentation.Xaml.ViewStateXamlHelper.ConvertViewStateToAttachedProperties(XamlReader inputReader, ViewStateIdManager idManager, Dictionary2& viewStateSourceLocationMap) at Microsoft.Activities.Presentation.Xaml.WorkflowDesignerXamlHelper.DeserializeString(String text, DeserializationMode mode, IList1& loadErrors, Dictionary2& sourceLocations) at Microsoft.Activities.Presentation.Xaml.WorkflowDesignerXamlHelper.DeserializeString(String text, IList1& loadErrors, Dictionary`2& sourceLocations)
at System.Activities.Presentation.WorkflowDesigner.Load()