public function activate() {

		$ret = false;
		if ( 'plugin' === $this->get( 'type' ) ) {

			$ret = activate_plugins( $this->get( 'update_file' ) );

		} elseif ( 'theme' === $this->get( 'type' ) ) {

			$ret = true;
			switch_theme( $this->get( 'update_file' ) );

		}

		if ( true === $ret ) {
			// Translators: %s = Add-on name.
			return sprintf( __( '%s was successfully activated.', 'lifterlms' ), $this->get( 'title' ) );
		}

		// Translators: %s = Add-on name.
		return new WP_Error( 'activation', sprintf( __( 'Could not activate %s.', 'lifterlms' ), $this->get( 'title' ) ) );

	}