Only redirects when logged into WordPress

Hi Support

We have an issue, after the user logs into DocCheck they’re redirected back to the same login page. For example the user logins in on this page: https://www.nordimet.de/nordimet-fachkreiszugang/ and is redirected back to the same page: https://www.nordimet.de/nordimet-fachkreiszugang/

However if the user is logged into WordPress the logging in and redirect works fine, the user is successfully redirected to the required page.

Any support will be appreciated

Thanks

The page I need help with: [log in to see the link]