Reverse thrust does not work

[twistedwings]

I cannot get reverse thrust to work.
If throttle input is lower than 1500us, ArduPilot sends 1500us to the esc.

ArduPlane 4.6.1
Matek F405-Wing

log file

[Allister (Allister Schreiber)]

You can either turn on reverse thrust using RCx_OPTION,64 and use a switch to turn on/off reverse thrust.

Or set USE_REV_THRUST to 1 and you’ll always have reverse thrust available. There’s other options for the bit mask so you could have it only on for ACRO, or landing, or whatever you want.

[twistedwings]

I have setup reverse thrust according to the documentation.
I use this setup:

But it does not work.