Hi Max That would suggest that the PayPal scripts which have all the code for PayPal Checkout are not loading. But that's not going to be the case generally that Mac / iPhone users can't use PayPal Checkout so is it possible that your Mac has something installed that might block JavaScript? In the very latest version the cart will retry for 30 seconds to load the scripts so it might also be worth trying that in case it's to do with the connection.