By default, cluster node running on Windows Server 2016 enter to quarantine state when the node connectivity has an issue. The lock period is 7200 sec. (that will be 120 minutes).
To force the node to normal state, on quarantine node open Windows powershell to execute cmd
Start-ClusterNode – ClearQuarantine
Quarantine node will back to normal (“UP”) status
If problem persist, please check on event viewer to identify the potential issue.