GabSoftware

I suggest the following correction in file Mlp_Translation_Metabox.php:

private function is_translatable_by_user( WP_Post $post, $blog_id ) {
		$blog_id = absint( $blog_id );

		$post_type = get_post_type( $post );
		if( $post_type === FALSE )
		{
			return FALSE;
		}

		$remote_post = $this->data->get_remote_post( $post, $blog_id );
		if ( isset( $remote_post->dummy ) && $remote_post->dummy === TRUE ) {
			return current_user_can_for_blog( $blog_id, 'publish_' . $post_type . 's' );
			//return current_user_can_for_blog( $blog_id, 'publish' );
		}
		//return current_user_can_for_blog( $blog_id, 'edit_post', $remote_post->ID );
		return current_user_can_for_blog( $blog_id, 'edit_' . $post_type . 's', $remote_post->ID );
	}

Original lines are commented.
That way it works perfectly. It corrects the capability “edit_post” to “edit_posts”, and also enables the translation for pages and custom post types.

I just checked: it appears that all the non super-admin administrators cannot display the meta box and do not have the option to do so. As soon as I grant super admin privilege on one particular user, this user suddenly have access to multilingualpress.

The user is administrator on all the sites.

As for my debugging code, you will find it below:

public function register_meta_boxes( $post_type, WP_Post $post ) {

		echo "Gab-MultilingualPress: enter register_meta_boxes\n";

		if ( ! in_array( $post_type, $this->allowed_post_types ) ) {
		  echo  "Gab-MultilingualPress: post is not in allowed_post_types\n";
			return;
		}

		$current_blog_id = get_current_blog_id();
		$site_relations = $this->plugin_data->get( 'site_relations' );
		$related_blogs = $site_relations->get_related_sites( $current_blog_id, FALSE );

		if ( empty( $related_blogs ) ) {
		  echo "Gab-MultilingualPress: empty related_blogs\n";
			return;
		}

		foreach ( $related_blogs as $blog_id ) {
			// Do not allow translations if the user is lacking capabilities for the remote blog
			if ( ! $this->is_translatable_by_user( $post, $blog_id ) ) {
			  echo "Gab-MultilingualPress: $blog_id is not translatable\n";
				continue;
			}

			if ( $current_blog_id !== (int) $blog_id ) {
				$this->register_metabox_per_language( $blog_id, $post );
				echo "Gab-MultilingualPress: register_metabox_per_language $blog_id\n";
			}
			else
			{
				echo "Gab-MultilingualPress: current_blog_id == $blog_id\n";
			}
		}

		$assets = $this->plugin_data->get( 'assets' );
		$assets->provide( array( 'mlp_admin_js', 'mlp_admin_css' ) );

		echo "Gab-MultilingualPress: exit register_meta_boxes\n";
	}

	/**
	 * Check if the current user has the appropriate capabilities to edit the given post.
	 *
	 * @param WP_Post $post
	 * @param int     $blog_id
	 *
	 * @return bool
	 */
	private function is_translatable_by_user( WP_Post $post, $blog_id ) {

		$blog_id = absint( $blog_id );

		$remote_post = $this->data->get_remote_post( $post, $blog_id );
		if ( isset( $remote_post->dummy ) && $remote_post->dummy === TRUE ) {
		  echo "Gab-MultilingualPress: current_user_can_for_blog publish" . current_user_can_for_blog( $blog_id, 'publish' ) . "\n";
			return current_user_can_for_blog( $blog_id, 'publish' );
		}

		echo "Gab-MultilingualPress: current_user_can_for_blog edit_post" . current_user_can_for_blog( $blog_id, 'edit_post', $remote_post->ID ) . "\n";
		return current_user_can_for_blog( $blog_id, 'edit_post', $remote_post->ID );
	}

That was just simple debugging, I haven’t made it very beautiful 🙂

I tried to network-deactivate the plugins except multilingualpress but still no luck. I tried to change the user role to something else then back to administrator, and that does not change. I’ll try to find what’s wrong.