Somebody use Unifi Network Application behind Authentik and NPM?

[springertje]

Hi All,

Running a selfhosted UNA (Unifi Network Application) environment.
Create in Authentik a Proxy Applictaion with Forward auth with the url for the UNA controller server ip and port 8443. (proxy host url created in NPM with a Let's encrypt ssl certificate).

Authentik and NPM are running on the same server, UNA on a other server.

I type in the url for the UNA , received first a login screen from authentik with TOTP (that's OK) ,and then been forwarded to the UNA url and get a login screen for UNA.(Also OK).

When tried to log in with my UNA account i get " Problem signing in,There was an error executing that request. Please try again later."

When i disable authentik , so i go directly to the UNA url then i can login without any problem.
Not to sure where to look.

Thanks in advance.