I use CustomPress, and have created several post types. Everything on the site is working great. I use Jetpack's sharing buttons.
However, on a single post view for my custom post types, the sharing buttons don't appear.
According to the Jetpack documentation, custom post types are supported, and supposedly on the Settings->Sharing page you should be able to check which custom post types show the sharing buttons. For me, that page is only showing the default custom post types.
I am using the most up-to-date version of Jetpack and CustomPress.