For loop terminates after the first iteration -Excel VBA - vba

Question

I am trying to do a simple loop, where I have declared some variables as array entries. I originally used them as variables to be overwritten, but changed it when I read that these variables will not automatically overwrite each time through the loop.
My problem is that this loop terminates after the first iteration (with no error). I can't seem to figure out why...
The code is essentially to find cons_sum(i,2) for each i, or row in the Pre-Summary sheet and sum some data in another sheet BOPE, then insert that sum into Pre-Summary.
This is my first post and I am teaching myself vba so please excuse any code fails.
This is my code:
Option Explicit
Sub Create_GAR080()
Consmonth = Sheets("GAR080").Range("B2").Value
Sheets("Pre-Summary").Select
LastRow_summary = Cells(Rows.Count, "A").End(xlUp).Row
LastRow = 156
LastCol = 16
Dim cons_sum() As Variant
ReDim cons_sum(LastRow_summary, 4)
For i = 1 To LastRow_summary Step 1
cons_sum(i, 1) = Cells(i, 2).Value & "" 'pulls participant
cons_sum(i, 2) = cons_sum(i, 1) & Cells(i, 1) ' participant and gas gate concatenated
If cons_sum(i, 1) = "BOPE" Then
Sheets(cons_sum(i, 1)).Select
cons_sum(i, 3) = WorksheetFunction.Match(cons_sum(i, 2), Sheets(cons_sum(i, 1)).Range("A:A")) ' find participant gas gate combo
cons_sum(i, 4) = Application.Sum(Sheets(cons_sum(i, 1)).Range(Cells(cons_sum(i, 3), 5), Cells(cons_sum(i, 3), 16)))
If cons_sum(i, 4) > 0 Then
Sheets("Pre-Summary").Cells(i, 4).Value = cons_sum(i, 4)
End If
End If
Next i
On Error Resume Next
End Sub

Answer 1

As Siddharth points out, your changing of sheets will result in cons_sum(i, 1) = "BOPE"to always be negative. Therefore, while the loop will run 1,848 times, it will not change anything.
In addition, a few more remarks:
You are using a 1848x4 array to do multiple operations in each line - but only stored the value of each operation and not use the array afterwards. Thus, you do not need 1848x4, but only 1x4, as you can reuse the variables
Instead of using an array, it is much better to use speaking variables. This will make your code much easier to understand
You have a lot of assumptions about the workbook structure hidden in the VBA formulas/statements, e.g. the number of rows, the name "BOPE", etc.. It is better to store them in constants in the beginning of the macro - or even better to store them somewhere on a settings sheets and refer to them with named ranges
You most likely forgot FALSE (or 0) as the third parameter for your match function. Therefore the function might return the wrong values if the column is not sorted
Instead of Range(Cells(x1,y1),Cells(x2,y2)) you can use Range.Resize and Range.Offset (and combinations thereof). This makes the code much easier to read!
do not use On Error Resume Next unless you know exactly what error you are happy to neglect! Even if you use it, use another On Error statement right after the operation that is allowed to produce an error.
Taking this into account, I reworked your code to the following:
Sub Create_GAR080_reworked()
Const cStrTerm As String = "BOPE"
Dim wsData As Worksheet
Dim lngRowCount As Long, i As Long
Dim strParticipantGasID As String
Dim lngParticipantGasCombo As Long
Dim dblSum As Double
Set wsData = Sheets(cStrTerm)
With Sheets("Pre-Summary")
lngRowCount = .Cells(Rows.Count, 1).End(xlUp).Row
For i = 1 To lngRowCount
If .Cells(i, 2) = cStrTerm Then
strParticipantGasID = cStrTerm & .Cells(i, 1) ' participant and gas gate concatenated
lngParticipantGasCombo = WorksheetFunction.Match( _
strParticipantGasID, wsData.Range("A:A"), 0) ' find participant gas gate combo
dblSum = Application.Sum( _
wsData.Range("E1:P1").Offset(lngParticipantGasCombo - 1))
If dblSum > 0 Then
.Cells(i, 4).Value = dblSum
End If
End If
Next i
End With
End Sub
As I do not have your worksheet, I couldn't debug it. Also, not sure if I hit the right names as I have no idea what each variable is really refer to. But it should give you a start.

Answer 2

If the first itiration the code Sheets(cons_sum(i, 1)).Select is hit, you'll never get back to the Pre-Summary sheet.
Try:
Option Explicit
Sub Create_GAR080()
Consmonth = Sheets("GAR080").Range("B2").Value
Sheets("Pre-Summary").Select
LastRow_summary = Cells(Rows.Count, "A").End(xlUp).Row
LastRow = 156
LastCol = 16
Dim cons_sum() As Variant
ReDim cons_sum(LastRow_summary, 4)
For i = 1 To LastRow_summary Step 1
Sheets("Pre-Summary").Select
cons_sum(i, 1) = Cells(i, 2).Value & "" 'pulls participant
cons_sum(i, 2) = cons_sum(i, 1) & Cells(i, 1) ' participant and gas gate concatenated
If cons_sum(i, 1) = "BOPE" Then
Sheets(cons_sum(i, 1)).Select
cons_sum(i, 3) = WorksheetFunction.Match(cons_sum(i, 2), Sheets(cons_sum(i, 1)).Range("A:A")) ' find participant gas gate combo
cons_sum(i, 4) = Application.Sum(Sheets(cons_sum(i, 1)).Range(Cells(cons_sum(i, 3), 5), Cells(cons_sum(i, 3), 16)))
If cons_sum(i, 4) > 0 Then
Sheets("Pre-Summary").Cells(i, 4).Value = cons_sum(i, 4)
End If
End If
Next i
On Error Resume Next
End Sub