Localhost sent an invalid response for my angular app

If changing to http does not work for you: in chrome, go to url: chrome://net-internals/#hsts

Under Delete domain security policies enter localhost or your problem domain and click the delete button on screen

You have to use the HTTP protocol instead, as you don't need to use a SSL Certificate.

Change it from:

https://localhost:8080

To:

http://localhost:8080

Then you should not have the error again.