Before using easyRates please make sure that Shopify market settings are configured for international shipping and selling.
If you want to exclude specific countries from shipping, create a custom market that includes only the countries you want to ship to.
If you would like any international shipping, it is recommended to just create an "International" market and add all of the countries. You can always choose which country to allow shipping in the "Shipping and Delivery" settings.
Please follow the instructions below to set up market settings in Shopify