This course was written for and recorded by Frontend Masters as the Complete Intro to React v4 and Intermediate React courses. The code here is licensed under the Apache 2.0 license and the course notes are licensed under the Creative Commons Attribution-NonCommercial 4.0 International license.
The Petfinder API was updated to v2. All course code still works, but you'll need to sign up for developer keys for the V2 of the Petfinder API (default if you are a new user). You'll also need to update your Petfinder Client (petfinder-client) to v2.0.1 in your package.json. See: https://github.com/btholt/complete-intro-to-react-v4/blob/master/package.json#L38
Parcel is an ever evolving project that's just getting better. If you run into problems with it not respecting changes (particularly to your .babelrc or .env files) then delete the dist/ and the .cache/ directories. You can do this in bash by running from the root directoy of your project rm -rf dist/ .cache/ or just by deleting those directories in your editor. This will force Parcel to start over and not cache anything.
See this issue for more specific instructions.
If you run into anything else, open an issue and we'll try to clarify or help.