Neither my finger and the phone screen is dirty. Registering fingerprint on this phone is quite hard even without any screen protector. Some of my finger got detected easily while some others not so lucky.
Now since i applied a hydrogel screen protector, it's impossible for the sensor to detect any of my finger.
This is a basic feature, used not only to unlock the phone but many app also use this feature. Please prioritize this matter in your update. Now i have to use password to login into my banking app.