From  https://docs.redhat.com/en/documentation/red_hat_jboss_enterprise_application_platform/8.1/html/configuration_guide/configuring_high_availability#disable_advertising_mod_cluster

Ensure that the EnableMCPMReceive directive exists 

EnableMCPMReceive was not corrected, which should be corrected to EnableMCMPReceive

Another error is that the MCPM should be MCMP.

I found that the EAP document from EAP 7.0 to EAP 8.1 has the same problems.

Please compare https://docs.redhat.com/en/documentation/red_hat_jboss_core_services/2.4.62/html/apache_http_server_connectors_and_load_balancing_guide/mod_proxy_cluster_example#set_up_proxy_example and https://docs.redhat.com/en/documentation/red_hat_jboss_enterprise_application_platform/8.1/html/configuration_guide/configuring_high_availability#disable_advertising_mod_cluster