Load balancing with HAProxy

Hi, i have a 3 node Percona Cluster and 2 HA-Proxys running, now i wanted to setup this: https://www.percona.com/doc/percona-xtradb-cluster/LATEST/howtos/haproxy.html

Sadly, my clustercheck always returns “503”, but I can see in Clustercontrol that the Cluster is fine and works perfectly. Is there something that needs to be changed with percona or the clustercheck script?