Actually, I see what you mean, it is a problem in the monitoring station master node, it wants to check old server IP even though edited, so they were paused as false alerts.
It is super easy to know if a node is online just visit winXX.yourservicedomain.com you will get a reply from IIS even if it is a rejection.
Then it just cna't reach win12 and win16 at all, we use NAGIOS for additional monitoring but it is not having a public interface yet.