Instr with RegEx - Runtime error 5017 (RegEx Code provided)

Hello,

I found the following Instr function with RegEx.

The code Always stuck at 'set found = regEx.Execute(SearchIn).

Can anyone help me what's wrong with it?

Note that I've also checked the Microsoft VBScript Regular Expressions (1.0 or 5.5) and still is giving the same error.

Public Function InStrRegEx(ByVal searchIn As String, ByVal searchFor As String) As Long
    Dim regEx As Object, found As Object
    If Len(searchIn) > 0 And Len(searchFor) > 0 Then
        Set regEx = CreateObject("VBScript.RegExp")
        regEx.Pattern = searchFor
        regEx.Global = True
        regEx.IgnoreCase = True
        Set found = regEx.Execute(searchIn)        <-----when debug, this is where it's shown
        If found.Count <> 0 Then InStrRegEx = found(0).FirstIndex + 1
    End If
End Function

NOTE: Was able to resolve by using "\\([0-9]+) ([0-9]+)\\" instead of "\## ####\"