OpenID authentication with FTN providers - dependency error

I need to authenticate users using FTN and started testing things out using Signicat’s test environment found here:

I setup the OAuth / OpenID client on the dashboard “Api Clients” and was able to set up Postman to request a new Authorization Code and Token flow. The issue is when I change the “Identity provider restrictions” on the OAuth / OpenID client settings to only show ‘ftn’ providers.
When I do it, I am properly redirected to a list of Finnish banks, I pick one, like “OP” and go thru all the forms, but at the end I am redirected to a signicat page that says:

Virhe tapahtui
Ole hyvä ja yritä uudelleen tai ota yhteys tukeen
Pyynnön ID	0HMI4E21SQ574:0000021C
Virhekoodi	IDH_30
Virhekuvaus	Dependency error

I cannot find any info anywhere about what this might be. I would appreciate any help!