Code Does Not Work When Change Column Value A To D

I have a macro that runs through a list and stores elements to an array. If the element is not found in my list, it adds to the next available row and adds the value from the array to that cell. Right now, I am searching in column d but am storing the value of column a at that location. When I switch the reference to column D, the value is not inserted into my new list.

Here is my current code:

Code:
Sub Arraytest()
Dim arr As Variant, lastrow As Long, i As Long, f As Long, l As Long, lastrow2 As Long, insertrow As Long

[Code].....

Why does the code not work properly when I switch to D? The value is storing correctly in the array. I test this by the last line of the code and it executes properly.