Error 2042 with Application.Match

Hello,

I am having some issues with a macro I wrote. I am getting the error 2042 and I know what that errors means but my code is correct and I passing the dates correctly but maybe some fresh eyes will help

Dim startDate As String
Dim vColumn As Variant
Dim rng As Range
Set rng = Worksheets("Output").Range("d10:aaa10")

startDate = InputBox("Enter the Start Date:  (mm/dd/yyyy)")
startDate = Format(startDate, "mm/dd/yyyy")

vColumn = Application.Match(startDate, rng, 0)