Marketpress + Stripe: Checkout Page Not Showing

Hi,
I'm running Marketpress + Stripe in test mode with Force SSL unchecked. Setup a test product.
All MP pages are working except the Checkout Page is blank.
I searched around and tried adding other content to the page to help generate the checkout info but that didn't work either. I added some other MP shortcodes and they displayed ok.
I don't have an SSL certificate yet, but as I'm only testing I thought this wouldn't be an issue just yet.
Any other ideas? Thanks.
Paul