When you import a CSV file using Power Query any extra rows are automatically included. Unfortunately, extra columns are NOT included. Here’s how to fix that.
In the image below I have the Formula Bar showing for the Source step for importing a CSV file.
I have highlighted the argument that specifies how many columns it will import. This argument is optional. You can edit in the Formula Bar and delete that argument. Then when you refresh the Power Query it will import all the columns in your CSV file, no matter how many there are.
Easy fix.