Weighted loadbalanced MultiWAN not working

[fathibn]

Hi, I have followed the document at https://docs.opnsense.org/manual/multiwan.html and setup a weighted monitored loadbalanced multiwan group between 2 adsl connections.
on the interfaces configuration page relative to the WAN interface (both adsl connections are on the same subnet but to two different isp), the gateway group doesn't appear. If i leave the Gateway vakue to its default, packets are not forwarded from the lan clients to the internet. If i choose any of the wan gateways traffic is forwarded from  lan clients to the internet but then i don't have load balancing.
Can someone help me please ?
TIA
Fathi B.N.