Troubleshooting
When developing electron apps there are two processes: main, and renderer. In this case main corresponds to electron-starter.js and its console is wherever you called npm run dev or electron . from. renderer corresponds to the React App - this is everything else. The react app's console is in the electron/browser window and can be seen by using dev tools to inspect the window. When running npm run dev, it should open by default.
Potential Issues
Package not found or other error related to npm
Try deleting your node_modules folder and the package-lock.json then running npm install then npm run rebuild.