The configured management IP address protocols determine whether IPv4 or IPv6 or both are enabled on the cluster. If a cluster does not have an IPv6 cluster address the IPv6 protocol stack will not be enabled, and therefore remote services such as email servers or SNMP servers cannot be accessed through an IPv6 address.
If you can only access the service through an IPv6 address and you need to continue to use the service, you will also have to continue to specify an IPv6 cluster address even if you do not intend to manage your cluster through this address.
Otherwise, re-configure the cluster so that all remote services use only IPv4 addresses, and resubmit the task to remove the IPv6 cluster address.