Then you can cancel with no notice period at all. German law requires providers who let you sign up online to offer a working cancellation button.
Courts confirmed this repeatedly in 2025 and 2026. A login wall before the button is not allowed. Neither are offers to keep you on the confirmation page.
We check every provider automatically and capture the evidence when a button fails.
Take a screenshot with the date visible.
If the button is defective, say so in your cancellation and state that you are terminating without notice on that basis.
§ 312k (6) BGB. General information about German law, not advice on an individual case.
Then you can cancel with no notice period at all. German law requires providers who let you sign up online to offer a working cancellation button.