I just came across this old post. Nothing listed above actually worked for me. I tested the script below, and it worked fine on my system. Sharing here, for the benefit of others who come here after me.
Sub RunPython()
Dim objShell As Object
Dim PythonExe, PythonScript As String
Set objShell = VBA.CreateObject("Wscript.Shell")
PythonExe = """C:\your_path\Python\Python38\python.exe"""
PythonScript = "C:\your_path\from_vba.py"
objShell.Run PythonExe & PythonScript
End Sub