Don't forget to create an .env.development file in the route of /client. The .env.development file should have include REACT_APP_BASE_URL=the-location-of-your-node-api
The server/.env file needs:
MONGO_URI=yourmongodbconnectionstring
CLOUDINARY_NAME=yourcloudinaryname
CLOUDINARY_KEY=yourcloudinarykey
CLOUDINARY_SECRET=yourcloudinarysecret