Hi,
I had the same error using VCB for full backou of linux VMs.
Procedure stopped to work with the message;
PORT is not set, defaulting to 443
failed to prepare erp for backup, PrepareForBackup() returned error 16
C:\Program Files (x86)\VMware\VMware Consolidated Backup Framework\backupexec\command.wsf(181, 😎 Microsoft JScript runtime error: 'name' is null or not an object
The problem was in DNS
The ip address of virtual center vc.domain.com for an unknow reason was removed from domain.com zone.
On the backup proxy server name resolution for vc was ok because the ip was set in hosts file, but backup started to work again only when vc was defined in DNS.
Valter