Locked out
I can't unlock my 12promax, because it doesn't leave the passcode numbers there for me to type them in, they disappear immediately...
Question marked as
When you swipe upwards to reveal the passcode screen if you are not using Face ID, it should remain long enough for you to tap the first number, then it should remain while you type in the rest. I would force restart the iPhone and the phone will reboot. Try after that. Force restart iPhone - Apple Support