Formula to copy data to new sheet works but gives an error when run

I am using a macro to copy data from multiple sheets referenced in a list of cells and place the data it one master sheet.

The formula works and gives me the output i want however every time i run it it finishes with an error of 'Subscript out of range'

Here is the code i'm using

Sub blanktemp()

Dim cell As Range
lastRef = Cells(Rows.Count, 24).End(xlUp).Row

For Each sheetRef In Range("X2:X" & lastRef)

    Sheets(sheetRef.Value).Select
    lastTest = Cells(Rows.Count, 2).End(xlUp).Row
    Range("A2:F" & lastTest).Copy
    
    Sheets("BlankTemplate").Select
    blankRow = Cells(Rows.Count, 2).End(xlUp).Row + 1 'use column 2 as at the mo nothing is in column1
    Cells(blankRow, 1).Select 'location to paste column 2, next empty row
    Selection.PasteSpecial Paste:=xlPasteValues, Operation:=xlNone, SkipBlanks _
:=False, Transpose:=False   

Next sheetRef

End Sub

Any help to fix the error would be apprciated