Problems with automatic engine start takeoff

I have tried to make an autonomous and not get off the engine starts with the parameters of TKOFF_THR_MINACC, TKOFF_THR_DELAY, TKOFF_THR_MINSPD. Could someone tell me if there is another variable that may be preventing the engine start ?

Assuming you’ve read this: plane.ardupilot.com/wiki/flight- … c-takeoff/

We use a bungee to launch and set most of the parameters to 0 which causes the motor to start as soon as Auto is engaged. As the launcher hears the motor start he launches, no start means the mission hasn’t started (or been restarted). Mission item takeoff pitch set to 10-14 degrees and altitude 50-80m depending on terrain.

A log file would really help us figure out your configuration and what’s not working.
Is the plane armed? You need a takeoff waypoint in your mission for it to auto takeoff.
Thanks, Grant.