Hey @Kiran62! Philippe here. I hope you're doing well.
I'll be happy to help you with your iPhone! Can/have you tried the following:
To make sure that the feature isn't turned off by any new update, follow these steps to check and ensure Touch ID is enabled on your iPhone 8:
Have you tried to restart the phone?
If that doesn't work, you can try resetting all settings.
Let us know if that helps.
Thanks very much
I have tried all these things but nothing worked out.
Although everything was fine and working before 20 days but somehow it stopped working, now i have to write my username and password eaverytime.