Issues with code sent from 2010 to 2016

After sending a form to use on my new computer I keep getting error/debug messages. I changed all the needed information in the code as to where the new form is to be saved etc. however this one line keeps coming up as being something wrong. The code works just fine in my 2010 Excel version but not at all in the 2016 update. Anyone know what I'm missing?

This is the highlighted area each time I try to save it:

[ActiveWorkbook.SaveAs NewFN, FileFormat:=xlOpenXMLWorkbook]

Full Module code reads as follows:

[Sub SaveInvoiceWithNewName()
    Dim NewFN As Variant
    ' copy invoice to a new workbook
    ActiveSheet.Copy
    NewFN = "C:\Users\Candice\Documents\WRI\Billings\" & Range("J12").Value & ".xlsx"
    ActiveWorkbook.SaveAs NewFN, FileFormat:=xlOpenXMLWorkbook
    ActiveWorkbook.Close
    NextInvoice
    ActiveSheet.Shapes("Textbox 8").TextFrame.Characters.Text = ""
End Sub]

Any help would be appreciated.
Thanks,
D