Hi @sunshine25, sorry to hear about this. 
Are there any error messages showing when you are trying to unlock the device using fingerprint? Make sure that the finger(s) you are using are not wet and there isn't any moisture on them.
You can also try to removing the fingerprint(s) and adding them again to see if you then are able to unlock the device using fingerprint again.
You can read more about how to do this on the link below.
https://support.sonymobile.com/global-en/xperiax/userguide/fingerprint-manager/
Let me know how it goes! 
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