If you just need to replace the images then you don’t even need a CSV. Without a CSV it will automatically run for all images in the folder.
With that said, it should still work. A single row CSV can be used if you only need to run some images in the folder and don’t want to run all of them.
There must be some kind of hidden data in the CSV. Please open the CSV in a plain text editor such as Notepad or TextEdit. Then post a screen shot of what the CSV looks like in the plain text editor. This will show any hidden characters or hidden row headers..