After I applied the software upgrade "security update" released in mid-August of 2021, I cannot open the Samsung pay app and it is stuck "Initializing". I have tried to forced stop, clear cache, clear data, reinstall the app from Google Play Store but nothing works.
I have a Galaxy S21 Ultra 5G, Android version 11, One UI version 3.1; Service provider AT&T
Phone settings - apps - samsung pay - storage - clear data
This is the reset way for your samsung pay. If you use samsung pay before, all the data will be lost.
Otherwise, restart your device first.