While navigating to the local version using URL [ Example : “http://<DOMAIN_NAME>/c.<ACCOUNT_ID>/<SSP_APPLICATION>/shopping-local.ssp” ] for viewing the customized Theme/Extension in a browser, You may see an error “Access to XMLHttpRequest at..[Local server URL ] from origin ..[Test domain].. has been blocked by CORS policy” or “Failed to load Resource error” in console.
This error is caused due to unsecured domain. To solve this error go to Commerce > Hosting > Domain and add SSL certificate to the test domain [ Note: Some test accounts will not support more than one secured domain].