There might be a problem with the checkout wizard in CC.2015 - when I run the wizard, the confirm_cart.php page ends up blank. I trashed the preferences and have now done this several times, same result every time. If I run the wizard in CC.2014, it works OK so I can now see the order confirmation section at the bottom of the checkout.php page and the card detail section appears when I click Continue, so all OK I think.
Another thing I should mention - in the cart wizard, In-Context Checkout is supposedly only available in the US only. I'm in the UK, but have found that if I don't check this box the Continue button on the checkout.php page doesn't work. With the box ticked, I get the Paypal popup.