You may not want to have all Jetpack modules active by default, so if you’ve gone through and deactivated the modules that you weren’t using – or someone else has, then you may have run into this problem.
You activated the Tiled Galleries and you can now see more Gallery options, but Slidehow isn’t one of them!
It turns out, you also need the Shortcode Embeds module to be active. To find this go to Jetpack > Settings in your WordPress admin, hover your mouse over the Shortcode Embeds module and click Activate.
If you head back over to your gallery and reload the page, you’ll see that Slideshow is now an option.