SPA React Demo Giving XHR Error

I’m following this demo: to try and get a provisional SPA set up for Okta login. I’ve cloned the repo, set the environment variables, and started the resource server (I am using the custom login page). However, when I try to log in (either with the username set in my bash profile, or with any of a number of users from my Okta directory) I get “there was an unexpected internal error. Please try again” and a NAME_NOT_RESOLVED error in the console. The frontend seems to be fine; I haven’t modified the source code at all, just added a testenv file with the required details, and I know they’re being set correctly in config. Has anyone run into this issue before? Thanks in advance.

Hi! I had the same issue with samples-js-angular.
It was all about CORS. This post helped me.