Access to fetch at ‘xxxxx’ from origin ‘xxxxxxx’ 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.
Go to Azure Portal -> Function App -> My Function App -> CORS
Make sure the Allowed Origins include the domain of the calling web app.
Use * for all origins.