Make sure you have installed [react-app-rewire] (https://github.com/timarney/react-app-rewired),
yarn add react-app-rewire-graphql-tag
in config-overrides.js:
const rewireGqlTag = require('react-app-rewire-graphql-tag');
module.exports = function override(config, env) {
conf = rewireGqlTag(config,env);
return conf;
}