VMware Cloud Director Availability 4.x.x
The internal communication on port 8048 ( TCP connection) between the tunnel appliance and the Cloud Director availability management appliance was broken.
To resolve the issue, restart the cloud service from the command line interface of the Cloud Director Availability.
systemctl status cloud.service
systemctl restart cloud.service
Note: After restarting the service, wait a couple of minutes for the service to become operational and display its service management interface again.
For more information to verify uptime and local and remote connectivity in the Cloud site, please see: Verify uptime and local and remote connectivity in the Cloud site
For more details on the VMware Cloud Director Availability ports requirements, please see: VMware Cloud Director Availability Network Ports.