Error on Lightbox mode

Datatrans wants to skip the redirect mode by October. I changed the settings accordingly in the Datatrans Rule, Lightbox appears, I am redirected to 3D Secure page, but the last step (confirm purchase page) does not appear, instead it ends up in an 404 errer (trying to access https://example.com/commerce_datatrans/processing/398/commerce_datatrans...)

Could this be related to the Datatrans Server settings or rather the module itself?

Thank you so much:-)
Matthias