Why does my ASP.NET webpage throw custom 404 error with certain file extensions

So, I have a folder on my server such like this:

You can access this resources by the URL:

https://83.53.92.229:44304/ServidorImagenes/image.png https://83.53.92.229:44304/ServidorImagenes/text.txt

But the kmz, instead of opening the file (maybe like the text in the xml, I'm not expecting to visualize it) it returns a custom 404:

https://83.53.92.229:44304/ServidorImagenes/track.kmz

Is there any way of allowing all files to be accessed without an error? Thank you very much.