haraldS-3

Problem:
If you're experiencing a critical error (white page) when editing a post with WPML activated, and WPML indicates that the REST API is not activated even though it is working, the issue might be related to the ACF Multilingual plugin.
Solution:
We recommend reinstalling the ACF Multilingual plugin with a fresh copy. You can download it from here.

If this solution does not apply to your case, or if it seems outdated, please check related known issues at https://wpml.org/known-issues/, verify the version of the permanent fix, and confirm that you have installed the latest versions of themes and plugins. We highly recommend opening a new support ticket if the problem persists. You can do so at WPML support forum.