Note 9 fingerprint sensor won't unlock the phone.

Unlock using second method, then delete your fingerprints and add them again.. Always use a backup method to unlock the device in case biometrics fail.
 
Don't know what's wrong with it but the RFPS won't unlock the phone.

I try to save my fingerprints when my fingers are really dry. This seems to work better than when I save them when they are not dry and then try to use the FP sensor when they are dry.