.find Function Failing

Excel Forum,

I am searching for the row number of a cell in column A that contains a specific value. My code is returning errors and after researching the issue I am still at a loss. I have tried cutting and pasting other programmers' code into my worksheet but that still fails. Any help will be greatly appreciated.

Below is my code and attached is the spreadsheet I am searching in. The portion that is failing me is in bold.

Thank you for your help.

  
With Sheets("12 mo inc det")
        .Select
        .Unprotect
        Columns("A:B").EntireColumn.Hidden = False
            Range("ah12").Value = "1"
            Range("ah12").Copy
                Columns("a:a").PasteSpecial Paste:=xlPasteAll, Operation:=xlMultiply
            Range("ah13").Select
            
        Dim keyRange As Range, keyRow As Range
            Set keyRange = Range("a1", Range("a65536").End(xlUp))
            Set keyRow = keyRange.Find(what:="4010", LookIn:=xlValues, lookat:=xlPart)
                If keyRow Is Nothing Then
                    MsgBox "not found"
                Else
                    MsgBox "found on row " & keyRow.Row
                End If
                         
        
    End With