Start with only one switch or sensor. I am guessing it is a permission issue. I had a similar problem. Make sure the folder custom_ui and all the files inside have been assigned to the user homeassistant (or whatever it is in your case).
I experience the same issue. Rights are ok, freshly downloaded the .html and .html.gz files to /www/custom-ui, but the lights are vanished from the frontend.
Use sudo chown -R homeassistant:homeassistant /home/homeassistant/.homeassistant/. This will change all the files/folders in /home/homeassistant/.homeassistant/ to homeassistant. You may have to change the path depending on your installation method.