Have you tried it as below, keep in mind you need to specify the name of the shared mailbox in the below code:
    Dim mynamespace As outlook.Namespace
    Dim strRowData As String
    Dim strDelimiter As String
    Dim myDestFolder As outlook.Folder
    Dim ShareInbox As outlook.MAPIFolder
    Dim SubFolder As Object
    Dim InputFolder As String
    Dim OutputFolder As String
    Dim ProdMail As String
    Dim SavePath As String
    Dim oXLApp As Object, oXLwb As Object, oXLws As Object
    Dim lRow As Long
    
    On Error Resume Next
    Set oXLApp = GetObject(, "Excel.Application")
    
    '~~> If not found then create new instance
    If Err.Number <> 0 Then
        Set oXLApp = CreateObject("Excel.Application")
    End If
    Err.Clear
    On Error GoTo 0
    
    '~~> Open the relevant file
    SavePath = "\\C:\Macro"
    Set oXLwb = oXLApp.Workbooks.Open(SavePath & "\Test.xlsx")
               
    'Extract Mailbox and subfolder details from a sheet named as "Folder Details"
    
    Set oXLws = oXLwb.Sheets("Folder Details")
           
    ProdMail = oXLws.Range("B1")
    InputFolder = oXLws.Range("B2")
    OutputFolder = oXLws.Range("B3")
       
       
    strRowData = ""
    
    ' Code to extract emails from specific subfolder within shared folder and copy the data across excel spreadsheet.
    Set mynamespace = outlook.GetNamespace("MAPI")
    Set ShareInbox = mynamespace.Session.Folders.Item("Name of shared mailbox") ' change to suit
    Set SubFolder = ShareInbox.Folders.Item(InputFolder) 'Change this line to specify folder
    Set myDestFolder = ShareInbox.Folders.Item(OutputFolder)
When I tested the above code the folders that I located were in a shared mailbox but outside of the shared mailbox inbox so to speak.