Yes, it must be something with administrator rights.
There is a problem with disk C: or D: but if I try to create a file on any other disk E: or F: it works.
Way this code dont work in accesds 2016
Private Sub C71_Click()
Set fs = CreateObject("Scripting.FileSystemObject")
Set a = fs.CreateTextFile("c:\testfile.txt", True)
a.WriteLine ("This is a test.")
a.Close
End Sub