I see you are using a custom theme, so difficult to say what might be wrong in the code. I would advise checking with your developer and making sure the correct language code is used when searching. if you need help with custom code you can hire a WPML contractor:
since the instructions and code are provided by the theme author, not us, and this theme is not on our official compatible theme list nor we have tested it, please contact the theme support and check further with them on why the code is not working and if they have another suggestion.
If they need help from our side, they can join our GoGlobal program and our devs will be glad to help them out.