Did you tap on the option when you first ever logged onto the site so your phone remembered the login ?
If not try logging out and then back in or go to your Security and Biometrics section and then Samsung Pass and see if you can manually add your login credentials @sarkar
Some apps I've come across in my past experience also do not allow for Samsung Pass to save login details.
Daily Driver > Samsung Galaxy s²⁵ Ultra 512Gb ~ Titanium Black.
The advice I offer is my own and does not represent Samsung’s position.
I'm here to help. " This is the way. "
