Unable to sign in with additional users

I am using the Okta developer portal configured with my application for OIDC. For the original developer account created with the developer instance, everything works perfect. I can log in through Okta and authenticate to my application with no issues. For any additional users I have added this does not work. I access the Okta login widget, enter my username and password, and then receive the message “Unable to sign in.” This happens with any additional user accounts I create. I fell like there is just a setting or configuration somewhere that I am missing that will enable these accounts to authenticate. What am I missing? Thanks!

Are these same additional users able to log into Okta directly or is the issue only occurring when logging into your OIDC application?

Have you tried checking the Okta System Logs for failures/events related to these users?

Yes, these users are able to log into the Okta dashboard directly. Once they are logged in there, they can also log into my application without authenticating again to Okta.

I’ve checked the system logs and don’t even see a record of the failed login attempt. I’m not sure what to make of that.

Are the users local Okta users? As in, do they have a password set in Okta, or are they redirected to an external IdP to log in instead?

Otherwise, can you also ensure that your users are being assigned to the OIDC application you created?

Yes the users are local Okta users and the OIDC application is assigned to them. If they are already logged into the Okta dashboard, it lets them in the application without any additional authentication. It’s only when they need to enter their username and password that the “Unable to sign in” problem occurs.

I’m creating the users by doing Directory > people > add user on Okta instance https://dev-28810421.okta.com/.