Instance Groups issue

Hi,
I try to install AWX 8.0.0 on two instances but when I run the ping command, the “Execution node” is always the same. In my case the execution node is always “awx”.

I have changed the CLUSTER variable in /etc/tower/settings.py with the name of my second host inside the AWX task and web containers and restart both.
I have provisionning this second host with awx-manage command to have my two instances in my group instance named “tower”.

From awx_web :

bash-4.2# awx-manage list_instances
[tower capacity=278 policy=100%]
awx capacity=301 version=8.0.0.0 heartbeat=“2019-10-29 12:24:44”
nameOfMySecondHost capacity=301 version=8.0.0.0 heartbeat=“2019-10-29 12:24:56”

I think this is an rabittmq issue but I don’t find the wrong parameter or variable that I need to change.
Could you help me ?

(Same issue with AWX 7.0.0)

Thanks in advance