Problem solved!
I have edited the file, and restart the computer.
sudo pluma /usr/share/dbus-1/system.d/org.freedesktop.UPower.conf
Line <allow send_destination="org.freedesktop.UPower.KbdBacklight"
Change to <deny send_destination="org.freedesktop.UPower.KbdBacklight"
Line <allow send_destination="org.freedesktop.UPower"
send_interface="org.freedesktop.UPower.KbdBacklight"/>
Change to <deny send_destination="org.freedesktop.UPower"
send_interface="org.freedesktop.UPower.KbdBacklight"/>
PS
Lenovo ThinkPad T450
Release 19.10 (Eoan Ermine) 64-bit
Kernel Linux 5.3.0-26-generic x86_64
MATE 1.22.2