Client won't connect to server after OS rebuild

I load an OS on a Win2k8 server, call it SVR1, then install Urbackup 1.4.8 client to it and do backups to a Urbackup Server 1.4.8 for a period of time. If I reload the server OS again, creating the same server name SVR1, IP, etc., when I reinstall the UrBackup client, it fails to find the UrBackup server. The icon stays red, and no status shows it found a backup server.

On the backup server, it shows the status of the SVR1 client never changes during the time the SVR1 server is off-line; and says it is ‘OK’, but it fails any attempts to do a scheduled backup of SVR1, as it had been doing previously.

The single backup server is configured to ‘push’ all controls to the clients, leaving only stopping a backup and choosing the files to backup available to the client configuration.

What’s causing the clients to fail to find the previously used backup server after installing a new OS?