The product Smart Baby Monitor is not being sold by Medisana for quite some time now and the App is not being maintained either. Which is why the App will not be receiving any updates and due to it not working with current iOS versions the App has been removed from the store.
We have tested some alternatives and had good results with the free app 'OWLR Foscam viewer' or 'OWLR IP Cam viewer'. Please try one of those apps. There are probably a lot of other apps that also work, but we could not test all of them.