https://wpml.org/errata/learndash-lms-certificate-preview-is-missing-in-the-editors-visual-tab/
LearnDash LMS - Certificate preview is missing in the Editor's Visual tab - WPML
Jan 8, 2021 - When WPML is active, you aren't able to preview LearnDash LMS certificates in the editor's Visual tab.
learndash lmscertificate preview