private static function _helper_subscription_activate() {
		$product_key = isset( $_GET['wc-helper-product-key'] ) ? wc_clean( wp_unslash( $_GET['wc-helper-product-key'] ) ) : '';
		$product_id  = isset( $_GET['wc-helper-product-id'] ) ? absint( $_GET['wc-helper-product-id'] ) : 0;

		if ( empty( $_GET['wc-helper-nonce'] ) || ! wp_verify_nonce( wp_unslash( $_GET['wc-helper-nonce'] ), 'activate:' . $product_key ) ) { // phpcs:ignore WordPress.Security.ValidatedSanitizedInput.InputNotSanitized
			self::log( 'Could not verify nonce in _helper_subscription_activate' );
			wp_die( 'Could not verify nonce' );
		}

		// Activate subscription.
		$activation_response = WC_Helper_API::post(
			'activate',
			array(
				'authenticated' => true,
				'body'          => wp_json_encode(
					array(
						'product_key' => $product_key,
					)
				),
			)
		);

		$activated = wp_remote_retrieve_response_code( $activation_response ) === 200;
		$body      = json_decode( wp_remote_retrieve_body( $activation_response ), true );

		if ( ! $activated && ! empty( $body['code'] ) && 'already_connected' === $body['code'] ) {
			$activated = true;
		}

		if ( $activated ) {
			/**
			 * Fires when the Helper activates a product successfully.
			 *
			 * @param int    $product_id Product ID being activated.
			 * @param string $product_key Subscription product key.
			 * @param array  $activation_response The response object from wp_safe_remote_request().
			 */
			do_action( 'woocommerce_helper_subscription_activate_success', $product_id, $product_key, $activation_response );
		} else {
			/**
			 * Fires when the Helper fails to activate a product.
			 *
			 * @param int    $product_id Product ID being activated.
			 * @param string $product_key Subscription product key.
			 * @param array  $activation_response The response object from wp_safe_remote_request().
			 */
			do_action( 'woocommerce_helper_subscription_activate_error', $product_id, $product_key, $activation_response );
		}

		// Attempt to activate this plugin.
		$local = self::_get_local_from_product_id( $product_id );
		if ( $local && 'plugin' == $local['_type'] && current_user_can( 'activate_plugins' ) && ! is_plugin_active( $local['_filename'] ) ) {
			activate_plugin( $local['_filename'] );
		}

		self::_flush_subscriptions_cache();
		self::_flush_updates_cache();

		$redirect_uri = add_query_arg(
			array(
				'page'                 => 'wc-addons',
				'section'              => 'helper',
				'filter'               => self::get_current_filter(),
				'wc-helper-status'     => $activated ? 'activate-success' : 'activate-error',
				'wc-helper-product-id' => $product_id,
			),
			admin_url( 'admin.php' )
		);

		wp_safe_redirect( $redirect_uri );
		die();
	}