The Gutenberg editor relies on the REST API, so both post types and taxonomies require the show_in_rest parameter be set to true when registering them. Your post type has this, but it’s missing from your taxonomy.
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The Gutenberg editor relies on the REST API, so both post types and taxonomies require the show_in_rest parameter be set to true when registering them. Your post type has this, but it’s missing from your taxonomy.