I'm using the basic Debut theme. I've noticed that when using Chrome on iOS and Android, my product pages don't automatically display Express checkout button (Paypal or Amazon) with the "more buying options" link.
Instead, you only get a BUY IT NOW button, and when you click through, you get the basic checkout process, the Express options don't show. If you ADD TO CART, and go to CART, then the Express options are there.
I get the correct purchase flow (i.e. Shopify chooses best Express option INSTEAD of BUY IT NOW) on PC Browsers (including Chrome) and also works fine on Safari mobile.
On the basis 90% of customers want express option, which encourages purchase, and 90% of my traffic is mobile, this is really important.
It seems to be very difficult to contact anyone directly at Shopify Support through their web site. When you follow links to contact them, you end up back here, or on their online documentation.