Here are some suggestions and explanations which may help. I suggest you read them and try out some of the solutions.
In passing, the Passcode will always required after an update or upgrade; if you have not used the App Store or iTunes store for a long time etc.
https://www.express.co.uk/life-styl...ne-Touch-ID-Fingerprint-Sensor-Passcode-iOS-9
https://forums.macrumors.com/thread...ord-for-store-but-have-touch-enabled.1976118/
Please post back.
Ian