Coroutine in VB.NET problem

Has implemented exactly as described, but get this error:

Error 3 Overload resolution failed because no accessible 'Start' can be called without a narrowing conversion:
 'Public Shared Function Start(
  coroutine As System.Func(Of System.Collections.Generic.IEnumerable(Of IdeaBlade.EntityModel.INotifyCompleted)), 
  [completedHandler As System.Action(Of IdeaBlade.EntityModel.CoroutineOperation) = Nothing]) 
  As IdeaBlade.EntityModel.CoroutineOperation': 
  Argument matching parameter 'coroutine' narrows 
   from 'System.Collections.Generic.IEnumerable(Of System.Func(Of IdeaBlade.EntityModel.INotifyCompleted))' 
   to   'System.Func(Of System.Collections.Generic.IEnumerable(Of IdeaBlade.EntityModel.INotifyCompleted))'. 

MY CODE IS AS FOLLOWS:
Can someone tell me whats wrong.

Function LoadAll(ByVal manager As myEntityManager) As IEnumerable(Of Func(Of INotifyCompleted))

' List of asynchronous functions for the Coroutine to execute serially
Dim funcList = New List(Of Func(Of INotifyCompleted))

' Get all
Dim loadFnc As Func(Of INotifyCompleted) = _
Function()
    Return manager.Customers.ExecuteAsync() ' return an INotifyCompleted
End Function

funcList.Add(loadFnc)

' return the list
Return funcList

End Function

' Sequence from my main routine

Dim op = Coroutine.Start(LoadAll(_eMgr))
AddHandler op.Completed, _
  Sub(s As Object, e As CoroutineCompletedEventArgs)
    If e.CompletedSuccessfully Then
      Debug.Write("All were loaded")
    Else
      Debug.Write(e.Error.Message)
    End If
  End sub