Thank you for reaching out to WPML support. While one of my colleagues reviews your ticket, I’d like to provide some initial guidance to assist you right away.
The message you're seeing is just a warning regarding the upcoming removal of support for Twig templates used in customizing language and currency switchers. As explained in our changelog here: https://wpml.org/changelog/2025/05/wpml-4-8-will-drop-support-for-twig-templates/, future versions of WPML will no longer support this method.