Run-time error '1004': autofill method of range class failed.

Could you please post your full code?

Sub AddNewLineNewJob()

    Range("A4").Select
    Selection.EntireRow.Insert , CopyOrigin:=xlFormatFromLeftOrAbove
    Selection.RowHeight = 18
    Rows("5:5").Select
    Selection.Copy
    Range("A4").Select
    ActiveSheet.Paste
    Range("D4:X4").Select
    Application.CutCopyMode = False
    Selection.ClearContents
   
    'Run macro to copy formulas on DDC sheet
   
    copy_formulae_DDC_Checklist
    Range("D4").Select

End Sub

Sub copy_formulae_DDC_Checklist()



'This macro updates the formulas on the 'DDC Checklist' sheet when a new row is inserted on the Input sheet.

Dim lastrow As Long

lastrow = Range("Y65000").End(xlUp).Row

    'Copy formulas
    Sheets("DDC Checklist").Select
    Range("Y7:AI7").Select
              'Selection.AutoFill Destination:=Range("Y7:AI506")
    Selection.AutoFill Destination:=Range("Y7:Y" & lastrow)
    Range("Y7:AI506").Select
     
    'Select Range A1 on DDC Sheet
    Range("A1").Select
   
    'Select Range A1 on Input Sheet
    Sheets("Input").Select
    Range("A1").Select
     
End Sub

Try below:

Sub AutoFill()
Dim Ws As Worksheet
Dim lastRow As Long
Set Ws = Worksheets("DDC Checklist")
lastRow = Ws.Range("Y" & Rows.Count).End(xlUp).Row
Ws.Range("Y7").AutoFill Destination:=Ws.Range("Y7:AI" & lastRow)
End Sub

Select allOpen in new window

Same error...

Are you running my code separately or you are calling from your original code?

Paste above code in your module and run macro AutoFill

I called it from the new line macro.  And I added the indented line...

Sub AutoFill()
Dim Ws As Worksheet
Dim lastRow As Long
Set Ws = Worksheets("DDC Checklist")
lastRow = Ws.Range("Y" & Rows.Count).End(xlUp).Row
       Ws.Range("Y7:AI7").Select
Ws.Range("Y7").AutoFill Destination:=Ws.Range("Y7:AI" & lastRow)
End Sub

Try below:

Sub AutoFill()
Dim Ws As Worksheet
Dim lastRow As Long
Set Ws = Worksheets("DDC Checklist")
lastRow = Ws.Range("Y" & Rows.Count).End(xlUp).Row
Ws.Range("Y7:AI7").AutoFill Destination:=Ws.Range("Y7:AI" & lastRow)
End Sub

Select allOpen in new window

It doesn't do anything w/out the select.

Have you tried with select?

I will.  Have to run to a meeting

You try without Select

It was a KB that caused the issue

What is KB?

Sorry, problem was not from my side, I did gave you solution.
Please assign points reasonably.

I wasn't trying to not give you points.  What I was trying to do was alert others of a possible issue that was not code related.  i don't need the points...