Not working on networks with static IP addresses

I have a pixhawk connected via static IP address and qmdnsengine is unable to find it, but avahi discovery works fine.
It appears that when qmdnsengine is using the mdns group `224.0.0.251` it does not work, but using `192.168.2.2` (rasp ip) or `192.168.2.255` works. Any idea ?