1. When you try to log in at the react screen, it will by default redirecting to http://localhost:1080/web to authenticate. So, if your PRPC is running on some other port ,go to (from pegaapp-react folder) \src\_services and edit the 'baseurl' in endpoints.js file to your localhost port.
2. In API service package, check Requires Authentication checkbox and uncheck Require TLS/SSL for REST services in this package
Let me know if you still face the issue or ignore if it already resolved
I notice that, in Step 7, you mention that you had turned Authentication off. You should leave the Authentication set to Basic and leave "Require TLS/SSL for REST services in this package" unchecked:
I was able to reproduce the problem you showed by unchecking "Requires authentication" but was able to log in and begin processing with the app successfully after re-checking "Requires authentication" and saving the api service package with the settings shown above.
If this doesn't work, please refer to these other suggestions in this post: