WeekNum VBA function doesn't output the value on specific computer - excel

Question

I was looking for an answer however I failed.
I wrote following code that basically adds a new row to the table and adds a current week number in 1st cell of new row:
Set table = Workbooks("EMEA Day 2 Chasing Audit Master Report.xlsm").Worksheets("Team Stats").ListObjects.Item("TableLilla")
Set oLastrowStats = Workbooks("EMEA Day 2 Chasing Audit Master Report.xlsm").Worksheets("Team Stats").ListObjects("TableLilla").ListRows.Add
Worksheets("Team Stats").ListObjects("TableLilla").ListColumns(1).DataBodyRange(oLastrowStats.Index, 1).Value = "W" & WorksheetFunction.WeekNum(Now, vbMonday)
The weird part starts here: the code works as it should on 2 computers but it does not on third one. On the 3rd computer, new row is added but the 3rd code line doesn't insert a week number.
I'm pretty sure it is related with this particular notebook, however have no clue where to look for solution. I didn't notice any major differences in Excel Settings. I've also checked the Win10 regional and date set up and they are the same as on my notebook.
Do you have any clue how to sort this out?
Thanks!

Answer 1

Try using a function that returns the ISO 8601 week number (and year):
' Constants.
Public Const MaxWeekValue As Integer = 53
Public Const MinWeekValue As Integer = 1
Public Const MaxMonthValue As Integer = 12
Public Const MinMonthValue As Integer = 1
' Returns the ISO 8601 week of a date.
' The related ISO year is returned by ref.
'
' 2016-01-06. Gustav Brock, Cactus Data ApS, CPH.
'
Public Function Week( _
ByVal Date1 As Date, _
Optional ByRef IsoYear As Integer) _
As Integer
Dim Month As Integer
Dim Interval As String
Dim Result As Integer
Interval = "ww"
Month = VBA.Month(Date1)
' Initially, set the ISO year to the calendar year.
IsoYear = VBA.Year(Date1)
Result = DatePart(Interval, Date1, vbMonday, vbFirstFourDays)
If Result = MaxWeekValue Then
If DatePart(Interval, DateAdd(Interval, 1, Date1), vbMonday, vbFirstFourDays) = MinWeekValue Then
' OK. The next week is the first week of the following year.
Else
' This is really the first week of the next ISO year.
' Correct for DatePart bug.
Result = MinWeekValue
End If
End If
' Adjust year where week number belongs to next or previous year.
If Month = MinMonthValue Then
If Result >= MaxWeekValue - 1 Then
' This is an early date of January belonging to the last week of the previous ISO year.
IsoYear = IsoYear - 1
End If
ElseIf Month = MaxMonthValue Then
If Result = MinWeekValue Then
' This is a late date of December belonging to the first week of the next ISO year.
IsoYear = IsoYear + 1
End If
End If
' IsoYear is returned by reference.
Week = Result
End Function
Like this:
Worksheets("Team Stats").ListObjects("TableLilla").ListColumns(1).DataBodyRange(oLastrowStats.Index, 1).Value = "W" & Week(Date)