For some of its functionality, WPML relies on the WordPress REST API. If the WordPress REST API is disabled, WPML will not be able to perform some of the communication with translation services or with our Advanced Translation Editor.
If you disable the WordPress REST API, some features in WPML will not work. WPML will not cause errors, but will report that these features are disabled.
WPML only accesses the REST API as an authenticated user. It never attempts to access the API without authenticating. The REST API also powers the WordPress Block Editor, so we consider it as 100% dependable and secure.
If you’ve globally disabled the REST API to tighten the site’s security, we recommend re-enabling and preventing anonymous external access to the API with a security plugin or some custom code.