Hi jason, thank for your answer I have had the same problem, I am just trying to connect with a API of the Interfuerza CRM, I cheked it in postman and works very good, but when I do the fetch from my .js file, i have the same error, please if you have any idea 
“Access to fetch at ‘https://app.interfuerza.com/api/v4/’ from origin ‘https://patri-test-store.myshopify.com’ has been blocked by CORS policy: Response to preflight request doesn’t pass access control check: No ‘Access-Control-Allow-Origin’ header is present on the requested resource. If an opaque response serves your needs, set the request’s mode to ‘no-cors’ to fetch the resource with CORS disabled.”