Divi won't show country selector options in checkout on Marketpress

The problem is on the checkout page. The Country field is blank, won't show options and won't let one proceed without an option. Live chat could not resolve. Problem is with the Divi theme interacting with MarketPress. (Quick switch to twenty-seventeen theme shows this.) By the way, I can force it to work by typing in "United States" and then hitting Enter key, but that is less than ideal. Can you help? Support access granted. I will have to switch to a new eCommerce plugin very, very soon if I can't get this to work.