public static function activated_plugin( $filename ) {
		$plugins = self::get_local_woo_plugins();

		// Not a local woo plugin.
		if ( empty( $plugins[ $filename ] ) ) {
			return;
		}

		// Make sure we have a connection.
		$auth = WC_Helper_Options::get( 'auth' );
		if ( empty( $auth ) ) {
			return;
		}

		$plugin        = $plugins[ $filename ];
		$product_id    = $plugin['_product_id'];
		$subscriptions = self::_get_subscriptions_from_product_id( $product_id, false );

		// No valid subscriptions for this product.
		if ( empty( $subscriptions ) ) {
			return;
		}

		$subscription = null;
		foreach ( $subscriptions as $_sub ) {

			// Don't attempt to activate expired subscriptions.
			if ( $_sub['expired'] ) {
				continue;
			}

			// No more sites available in this subscription.
			if ( $_sub['sites_max'] && $_sub['sites_active'] >= $_sub['sites_max'] ) {
				continue;
			}

			// Looks good.
			$subscription = $_sub;
			break;
		}

		// No valid subscription found.
		if ( ! $subscription ) {
			return;
		}

		$product_key         = $subscription['product_key'];
		$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 ) {
			self::log( 'Auto-activated a subscription for ' . $filename );
			/**
			 * 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 {
			self::log( 'Could not activate a subscription upon plugin activation: ' . $filename );

			/**
			 * 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 );
		}

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