Getting error 'object variable or With block variable not set' when trying to run sub - excel

Question

I did not create the code but am trying to troubleshoot an excel file and the original author is not available (layed off from company and not willing to help).
The following line is generating the error, 'object variable or With block variable not set'
Private Sub Workbook_Open()
Sheet1.Starttimer
End Sub
I looked at Sheet1 code and found the below, so I'm not sure what the problem is:
Sub Starttimer()
Application.DisplayAlerts = False
If Not Sheet4.ListObjects(1).DataBodyRange Is Nothing Then
Sheet4.ListObjects(1).DataBodyRange.Rows.Delete
End If
ActiveWorkbook.RefreshAll
Application.Calculate
SetProductionZeros
ActiveWorkbook.Save
ThisWorkbook.Close
End Sub
UPDATE
After setting the debug to break on all errors, the line that causes the error appears to be "r = Sheet4.ListObjects(1).DataBodyRange.Rows.Count" from the sub below:
Sub SetProductionZeros()
Dim tb1 As ListObject
Dim x As Long
Dim y As Long
Dim r As Long
Dim c As Long
'Set path for Table variable'
Set tb1 = Sheet4.ListObjects(1)
Sheet4.Activate
r = Sheet4.ListObjects(1).DataBodyRange.Rows.Count
c = Sheet4.ListObjects(1).DataBodyRange.Columns.Count
'Loop Through Each DataBody Row in Table
For y = 1 To r
'Loop Through Each Column in Table
For x = 1 To c
If IsEmpty(Sheet4.ListObjects(1).DataBodyRange.Cells(y, x)) Then Sheet4.ListObjects(1).DataBodyRange.Cells(y, x) = 0
Next x
Next y
Sheet4.Columns(5).EntireColumn.Delete
Dim lastrow As Long, lastcol As Long, thiscol As Long
Dim totalrow As Long, totalcol As Long, thisrow As Long
totalrow = 7 + Sheet4.ListObjects(1).Range.Rows.Count
totalcol = 2 + Sheet4.ListObjects(1).Range.Columns.Count
On Error GoTo Errorcatch
'lastrow = Cells(Rows.Count, 1).End(xlUp).row
'lastcol = Cells(1, Columns.Count).End(xlToLeft).Column
Sheet4.Cells(totalrow, 3).Value = "Total"
For thiscol = 5 To totalcol - 1
Sheet4.Cells(totalrow, thiscol).Select
ActiveCell.Value = WorksheetFunction.Sum(Sheet4.Range(Sheet4.Cells(1, ActiveCell.Column), ActiveCell))
Next
Sheet4.Rows(totalrow).Font.Bold = True
Sheet4.Cells(7, totalcol).Value = "Total"
For thisrow = 8 To totalrow
Sheet4.Cells(thisrow, totalcol).Select
ActiveCell.Value = WorksheetFunction.Sum(Sheet4.Range(Sheet4.Cells(ActiveCell.row, 5), ActiveCell))
Next
Sheet4.Columns(totalcol).Font.Bold = True
'Sheet4.Columns(2).HorizontalAlignment = xleft
For y = totalrow To 8 Step -1
If Sheet4.Cells(y, 2) = "T" And Sheet4.Cells(y, totalcol).Value = 0 Then
Sheet4.Rows(y).EntireRow.Delete
End If
Next
Exit Sub
Errorcatch:
MsgBox Err.Description
End Sub

Answer 1

Follow the logic:
When you open the workbook, you call Sheet1.StartTimer
Sheet1.StartTimer includes
If Not Sheet4.ListObjects(1).DataBodyRange Is Nothing Then
Sheet4.ListObjects(1).DataBodyRange.Rows.Delete
End If
At this point Sheet4.ListObjects(1).DataBodyRange will be Nothing (because you deleted all its rows)
Then you call SetProductionZeros
SetProductionZeros includes r = Sheet4.ListObjects(1).DataBodyRange.Rows.Count
But because Sheet4.ListObjects(1).DataBodyRange is Nothing this throws an error. (Same applies to .Columns.Count)
You can wrap references to DataBodyRange in
If Not Sheet4.ListObjects(1).DataBodyRange Is Nothing Then
' ...
End If
but you need to consider what you want to achieve when there are no rows in Sheet4.ListObjects(1)

Answer 2

This error seems to indicate that you are assigning an object to r without set. Nothing is an object. So in your case you are likely getting Nothing from Sheet4.ListObjects(1).DataBodyRange.Rows.Count. After Set tb1 = Sheet4.ListObjects(1), verify that tb1 is not nothing.
FYI, For code clarity, you should be using r = tb1.DataBodyRange.Rows.Count (same for c =).