How to get authenticated with OAuth in REST API

I have implemented a REST-API  with API designer to be consumed by the users to Get and POST data to the system.

Until now The user authenticates using RoleBasedPerson calling first the POST Request imx/login with their credentials in the Body, e.g.:

{"Module": "RoleBasedPerson", "User": "MyUser", "Password": "MyPW"}

Now we want to let authenticate the users with OAuth.

I'm able to get an id_token and also an access_token from the Identity provider in Postman and I try to do the POST request  {{baseUrl}}/imx/login/:appId with something like this in the Body


The response I get is : "Message": "An error occurred while processing your request."

The Log file in IIS : Failed to authenticate user using OAuth2/Open ID Connect. VI.Base.ViException: Missing id_token.

in Designer I already configured the OAuth 2.0 using the wizard and my OpenID Connect metadata document

In API Designer I already added the AuthModule OAuthRoleBased

Do you have a hint what I'm doing wrong?

Thanks in advance