Apache reverse proxy failover

Question

We are using an Apache reverse proxy at my work that redirect requests to multiple in-house websites, and employees can acccess all these services via VPN. We currently have 2 different internet service providers for failover reasons, but can't seem to make the failover work in httpd. Would anyone mind taking a look ?

This is the mod_proxy for load balance / failover configuration :

<Proxy balancer://mycluster>

    BalancerMember http://xxx.xxx.xxx.xxx  retry=30 
    
    BalancerMember http://yyy.yyy.yyy.yyy status=+H retry=0
</Proxy>
ProxyPass / balancer://mycluster/ lbmethod=byrequests stickysession=JSESSIONID|jsessionid

<VirtualHost *:80>

ServerAlias "site 1"
ServerAlias "site 2"
ServerAlias "site 3"
    
<Proxy balancer://mycluster>
    # ISP 1
    BalancerMember http://xxx.xxx.xxx.xxx  retry=30 
    # ISP 2
    BalancerMember http://yyy.yyy.yyy.yyy status=+H retry=0
</Proxy>

The same configuration is done for port 443.

When ISP 1 (xxx) goes down (which unfortunately happens often), the failover (yyy) doesn't seem to work or take over. This configuration has been done by my predecessor a long time ago.

Is there any other command line missing to activate the failover in case of ISP failure ?

Thank you