You may not have biometrics login working if you didn't authorize its use when you first logged in.
On iPhone :
go to Phone Settings
search for Bilderlings
Notifications
Face ID (or Touch ID).
For Android (the process may vary from device to device):
Phone settings
App settings
App settings
All apps
Bilderlings
Enable biometrics.
Once activated in the phone settings, go to the app settings and enable the feature.