Run-time error '438': Object doesn’t support this object or property with GetOpenFilename

The following worked on my old installation of Outlook 2016 so it must be either a small typo or there is something wrong with the references.

The code is in Outlook 2016:

Sub Sample()
    Dim myFile As Variant
    Dim i As Integer

    'Open File to search
    myFile = Application.GetOpenFilename(MultiSelect:=True)

    If IsArray(myFile) Then  '<~~ If user selects multiple file
        For i = LBound(myFile) To UBound(myFile)
            MsgBox myFile(i)
        Next i
    Else '<~~ If user selects single file
        MsgBox myFile
    End If
End Sub

I get:

for this line:

myFile = Application.GetOpenFilename(MultiSelect:=True)

Here are my selected references:

I was able to get your test working (In Outlook 365) by doing the following:

• Enable the Excel Object Reference Library 16.0 in the VBE
• Create a variable and set it as Excel.Application
• Use this variable to qualify the GetOpenFilename method.

Sub Sample()
    Dim myFile As Variant
    Dim i As Integer
    Dim myApp As Excel.Application
    Set myApp = New Excel.Application

    'Open File to search
    myFile = myApp.GetOpenFilename(MultiSelect:=True)

    If IsArray(myFile) Then  '<~~ If user selects multiple file
        For i = LBound(myFile) To UBound(myFile)
            MsgBox myFile(i)
        Next i
    Else '<~~ If user selects single file
        MsgBox myFile
    End If
End Sub

Be Aware

This creates a new instance of the Excel application for the duration your code is running.