When login in through itsme on the Izimi app, it can sometimes happen that your phone decided to open Izimi in your browser (Chrome or Safari) instead of continuing in the Izimi app itself.
If you use iOS, you can open your browser and go to app.izimi.be and in the top click on the banner that you want to open the Izimi app. Most of the time, restarting your phone solves this issue.