Arming gesture not working?

I am setting up my drone with a pixhawk4mini I had flying around. All seems to be working quite well (Sensors, GPS, ESC’s, remote is callibrated using QGC…) but I am not able to arm it via the throttle/yaw stick. If i assign an arming channel, it works fine, however I do not like that solution. Do you have any idea where I could look for the problem?