Autotune as a flight mode

About the Autotune , we can read in the online documentation ( Advanced Configuration » Tuning » AutoTune ->Additional Notes : In Copter-3.3 (and higher) AutoTune can be setup as a flight-mode. Switching into or out of the AutoTune flight mode responds in the same way as raising or lowering a ch7/ch8 aux switch high assigned the AutoTune function.
I’m flying with the firmware 3.4.4 , and have set a flight as autotune with MP to use it; But switching into this mode as no effect and the log records an error Subsys 10 (the vehicle was unable to enter the desired flight mode) and Ecode 15.

Were you in Stabilize or AltHold modes when you tried to enter AutoTune?

No , I have switched the flights from Loiter to Autotune. I did not understand that the previous flight mode before the switch is important. Il will test again. Thanks !!

After a new test , I confirm we have to fly in Stab or AltH before switching to autotune . Thanks .