Hi Felix,
Do you have the API Access Management feature activated in your production Org?
The feature is enabled out of the box in Okta Dev instances but not in paid for production tenants.
Also realize the the “default” auth server is just the name of the pre-configured custom authorization server and may or may not exist in your Okta tenant. Either it doesn’t exist because you don’t have the API access Management feature, it was renamed or Deleted, or it is only assigned to specific clients and not the client you are testing with.
Unless you need custom scopes or claims, I’d recommend using the Okta Org Auth Server rather than the default custom auth server. It is included in the basic Okta license and is not an additional feature like custom auth servers which are a part of the API Access Management feature. In other words using the Okta Org Auth server doesn’t cost anything while using the “default” server costs additional user licenses.
You can get the metadata for the Org Auth server with this URL
https://{{envUrl}}.okta.com/.well-known/oauth-authorization-server
Or get specific details for your client app with
https://{{envUrl}}.okta.com/.well-known/oauth-authorization-server?client_id={{clientId}}
Same thing for OIDC just substitute “oauth-authorization-server” with “openid-configuration”
Take a look at this article.
https://support.okta.com/help/s/article/Difference-Between-Okta-as-An-Authorization-Server-vs-Custom-Authorization-Server?language=en_US