"Arming denied: switch to manual mode first"

PX4 Autopilot Configuration & Flight Modes ⚙️
1

I’m starting the drone in takeoff mode, QGC shows that it’s ready to arm, I switch the arming switch, and arming is denied with error message “Arming denied: switch to manual mode first”.
What can be the problem?

Or is it impossible to arm while in takeoff mode?

2

You have to switch to manual mode first, e.g. Manual, Altitude control, or position control. Otherwise you can’t arm using the switch.