Hi,
I had the same issue too.
I use a Pixhawk 4 (FW 1.13.1) connected to a companion computer via serial connection,
then over wifi with mavproxy to the gcs, running QGroundcontrol. And I use the generic quad airframe.
I had to update mavproxy.py to the newest version and QGCS to the new daily (Oct 20th) version.
And I had also set the parameter to SYS_CTRL_ALLOC=1. Then it works for me.