why does this macro fail when f I copy and paste the exact same formula into the cell the formula works perfectly? (this is just one line of a larger macro but this is where it is getting stuck)

Sub test1()
ActiveCell.Formula = "=IF(Q2<>0,Q2,IF(ISNA(VLOOKUP(B2,[picks.xlsx]Sheet1!$A:$D,4,0)),"",IF(VLOOKUP(B2,[picks.xlsx]Sheet1!$A:$D,4,0)<>0,VLOOKUP(B2,[picks.xlsx]Sheet1!$A:$D,4,0),"")))"
End Sub
Thanks