Pixhawk 2 - esc not calibrate

Hello I would like to ask for advise. I finally get to the calibration of the pixhawk cube board whi I bought decemeber 2017 ( CubeBlack 002B0024 3136510C 34313630). And I have similar problem to this archived topic Pixhawk 2 - only 1 esc not calibrating .ESC no.1 won’t calibrate, other five are ok and spining. I would like to ask whaht can be the solution , If I still need to use the workaround with SERVO5_FUNCTION and how, when I have hexacopter and RC 5 is booked?
thank you.