hi friends Pin 8 not turn on for heated bed (1 reply)

my board is KFB 3.0
all is active(endstops - probe z - bed leveling)
but heated bed on pin 8 not power
This shows the error:

start
Printer is now online.
echo:Marlin 2.0.5
echo: Last Updated: 2020-03-14 | Author: (none, default config)
echo:Compiled: Jul 2 2023
echo: Free Memory: 5587 PlannerBufferBytes: 1136
echo:Hardcoded Default Settings Loaded
echo: G21 ; Units in mm (mm)
echo:; Filament settings: Disabled
echo: M200 D1.75
echo: M200 D0
echo:; Steps per unit:
echo: M92 X100.00 Y100.00 Z400.00 E98.20
echo:; Maximum feedrates (units/s):
echo: M203 X300.00 Y300.00 Z5.00 E25.00
echo:; Maximum Acceleration (units/s2):
echo: M201 X1000.00 Y1000.00 Z50.00 E10000.00
echo:; Acceleration (units/s2): P R T
echo: M204 P1500.00 R1500.00 T1500.00
echo:; Advanced: B S T J
echo: M205 B20000.00 S0.00 T0.00 J0.01
echo:; Home offset:
echo: M206 X0.00 Y0.00 Z0.00
echo:; Auto Bed Leveling:
echo: M420 S0 Z0.00
echo:; Z-Probe Offset (mm):
echo: M851 X10.00 Y10.00 Z0.00
Error:Thermal Runaway, system stopped! Heater_ID: bed
[ERROR] Error:Thermal Runaway, system stopped! Heater_ID: bed

Error:Printer halted. kill() called!
[ERROR] Error:Printer halted. kill() called!

Guide me
thanks