OAuth2.0 connection 400 - refresh BEFORE authorize

We have an issue with OAuth2.0 connection to our backend. Failed to verify connection 400. We see that verify connection goes through “refresh”, and refreshToken is empty, that’s why 400 occurred.
It looks like the flow is authorize → refresh instead of authorize → token → refresh. And that’s why refreshToken is empty.
Anybody an idea how to resolve this?

Did you ever figure out your problem with this? I am having the same problem.