Range.EntireColumn doesn't function properly, what is wrong with my code?

My code follows:

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When I Run the code I thought it was supposed to highlight the entire column A, but instead it highlights columns A to F which consists of my entire table.

But when i try using .EntireRow like this:

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The code works as how I would want it and it highlights the entire first row. What am I doing wrong here? What did i do wrong with the .EntireColumn function?

Nevermind, solved it already. Merged columns are the culprit.