What happens if the PPA core management node fails?
In case the PPA management node comes back online, how does it sync back with the service nodes?
Management node provides the tools to tune and manage the web services.
If web hosting, mail server, slave DNS, DB server are configured on service nodes which are online, then PPA will provide mentioned services. Websites and mail will stay available. In case if the Management Node itself had any hosting-related role, this one will be down. Also webmail service will be down most probably as it is usually hosted on a Management Node.
Management node checks service nodes availability once in five minutes. If the connection to service node was not established, its "Current state" will change to "off" in "Infrastructure" - "Service Nodes".