I have to run my code several times for it to execute entirely

I'm not sure whether it's because I'm using a mac or the code is wrong, but the rows aren't identifying properly, and therefore not deleting or pasting it into the other spreadsheet. I have to run the code three times for it to properly go through it and copy/paste and delete the cells into the other spreadsheet.

Many thanks!

here is the code:

Dim j, lastidno As Long


Sheets("Part B + C Modules").Activate
lastidno = Range("A2", Range("A2").End(xlDown)).Count + 1
For j = 2 To lastidno
If Range("O"& j) = "" Then
Sheets("Part B + C Modules").Range("A"& j).Copy
            Sheets("No Options Selected").Select
            NextRow = Cells(Rows.Count, 1).End(xlUp).Row + 1
            Cells(NextRow, 1).Select
            ActiveSheet.Paste
            Sheets("Part B + C Modules").Activate
Rows(j).EntireRow.Delete
End If
Next

MsgBox "done"
End Sub