react oidc-client token timout signinSilent error

Question

I was following the guidelines here to implement oidc-client with react: https://medium.com/@franciscopa91/how-to-implement-oidc-authentication-with-react-context-api-and-react-router-205e13f2d49

I got it working okay. But once I left the site idle for a couple hours, I noticed this in the console log:

I'm not exactly sure why I'm getting this, but I know it's happening somewhere in the following snippet in the authService.js file (from the article):

    signinSilent = () => {
        this.UserManager.signinSilent()
            .then((user) => {
                console.log("signed in", user);
            })
            .catch((err) => {
                console.log(err);
            });
    };

Has anyone else run into this issue or know how to properly implement a signinSilent() to work without an error and reacquire the new token when it times out?

I hope this is enough info, I'm not allowed to show anymore than this.