VBA Split() function not working when ":" is the delimiter - excel

Question

I'm trying to use the split() function to loop through a specified range and split all strings when a ":" is encountered, and replace the existing value with the split value.
Dim k As Integer
Dim lRow as Long
Dim startZip_col As Long
Dim startZip_str As String
Dim startZip_result() As String
Dim startZip_decomposed As Variant
For k = 2 To lRow
startZip_str = Cells(k, startZip_col).Value
startZip_result = Split(startZip_str, ":")
For Each startZip_decomposed In startZip_result
Cells(k, startZip_col) = startZip_result(1)
Next
Next k
a example of the values i want to split are:
abc:1234
abc:5678
def:3456
tried debug.print to pinpoint where the errors are, but column value is correctly identified, loop looks fine, not sure where went wrong

Answer 1

Logic:
Where is lRow. startZip_col inititalized? Define and initialize your variables/Objects correctly.
Fully qualify the cells else it may refer to active sheet which may not be the sheet you think it is. For example ws.Cells(k, startZip_col).Value where ws is the relevant worksheet.
Before splitting, check for the existence of :
Code:
Option Explicit
Sub Sample()
Dim ws As Worksheet
Dim lRow As Long
Dim i As Long, j As Long
Dim ZipCol As Long
Dim ZipString As String
Dim ZipResult As Variant
'~~> Change this to the relevant sheet
Set ws = Sheet1
'~~> Change this to the releavant column
ZipCol = 1
With ws
'~~> Get the last row in Col A. Change to relevant column
lRow = .Range("A" & .Rows.Count).End(xlUp).Row
For i = 2 To lRow
ZipString = .Cells(i, ZipCol).Value
'~~> Check if the string contains ":"
If InStr(1, ZipString, ":") Then
ZipResult = Split(ZipString, ":")
'.Cells(1, ZipCol) = ZipResult(1)
'~~> For testing
For j = LBound(ZipResult) To UBound(ZipResult)
Debug.Print ZipResult(j)
Next j
End If
Next i
End With
End Sub