How to fix 'Run-time error '1004' PasteSpecial - excel

Question

I have a file (called original) that has partially information for each row. Each row has a file name column (from where information is to be captured from).
For each row I'd like to open up the file in the file name column, and grab information from certain rows.
In the file it is only one column, with rows "Supplier Number : _____", the location of this row is variable, so I'd like to iterate through each row in the file to copy this cell value and paste it into the original file in the corresponding row.
This is what I have so far:
Const FOLDER_PATH = "C:\Users\[user]\Downloads\"
Sub iterateThroughAll()
ScreenUpdating = False
Dim wks As Worksheet
Set wks = ActiveSheet
Dim source As String
Dim target As String
Dim update As String
Dim rowT As Integer
rowT = 2
rowTT = 1
Dim rowRange As Range
Dim colRange As Range
Dim rowRangeT As Range
Dim LastCol As Long
Dim LastRow As Long
Dim LastRowT As Long
LastRow = wks.Cells(wks.Rows.Count, "A").End(xlUp).Row
Set rowRange = wks.Range("A2:A" & LastRow)
'Loop through each row
For Each rrow In rowRange
source = FOLDER_PATH & wks.Cells(i, 18).Value 'the name of the file we want to grab info from in this Column, always populated
'if the cell is empty, search through the file for "Supplier Number : "
If IsEmpty(wks.Cells(rowT, 19)) Then
Set wb = Workbooks.Open(source)
wb.Activate
LastRowT = Cells.Find("*", searchorder:=xlByRows, searchdirection:=xlPrevious).Row
Set rowRangeT = wks.Range("A1:A" & LastRowT)
For Each i In rowRangeT
If InStr(i.Cells.Offset(rowTT), "Supplier") > 0 Then
Range("A" & rowTT).Select
Selection.Copy
Windows("Get Supplier Number.xlsm").Activate
Range("A" & rowT).Select
wks.Paste
Else
rowTT = rowTT + 1
End If
Next i
wb.Close
Next rrow
ScreenUpdating = True
End Sub
I get the pastespecial error 1004.
What is expected is that for each row in "Get Supplier Number.xlsm", the row's A column is updated with the information
Thank you for helping!

Answer 1

First of all you should get rid of Activate and Select methods. You don't have to use them and they give nothing to your code. Using them is not a good approach.
To avoid them you should use specific references. Which you are doing so, until a specific point. Inside the for loop, after setting the wb, replace everything with the following:
With wb.Worksheets(1)
LastRowT = .Cells.Find("*", searchorder:=xlByRows, searchdirection:=xlPrevious).Row
Set rowRangeT = .Range("A1:A" & LastRowT)
For Each i In rowRangeT
If InStr(i.Cells.Offset(rowTT), "Supplier") > 0 Then
.Range("A" & rowTT).Copy wks.Range("A" & rowT)
Else
rowTT = rowTT + 1
End If
Next i
wb.Close
End With
I think this should do the job for you.
PS: If you need just the value of the cell in the opened workbook, then you could replace the Copy line with a simple equality:
wks.Range("A" & rowT) = .Range("A" & rowTT)