a) Pattern, PIN or Password security unlocking is required after the device restarts. Fingerprint unlock does not function at this point but it will work again after unlocking using another method.
b) Make sure there are no stains such as water or sweat on the fingerprint sensor. If there are, wipe the screen and try again.
c) Try to re-enter your fingerprint to your device by accessing “Settings”->“Security & biometrics”->“Fingerprint”->confirm your pattern/PIN/Password security lock->“Add fingerprint”.
d) Try to reset or update your device. (Refer to Q How can I perform a factory reset on my phone & Q How can I upgrade my device).
If the previously described options do not help, you can contact our hotline or repair center to get more professional technical assistance. Find the hotline or repair center information from the TCL website or APP “Support center”.