Here is a quick list of settings to check for which may cause your custom file names to not work:
- In Marketing =>SEO Tools section, make sure the “Custom File Names” checkbox is checked.
- In the Marketing =>SEO Tools section, make sure you clicked the “Update File Names” button
- Make sure there are no capital letters in the custom file name.
- Make sure there are no spaces in the custom file name.
- Make sure there are no ‘/’ (forward slashes) in the custom file name.
- Make sure the custom file name has an actual extension at the end like *.html, .asp, etc.