do you have this issue only for one VM,if yes that means the ports are configured properly between Vmware backup host and the VCenter and ESXI servers
is there any issue on this VM, (low space on local disks inside the vm,datastore low space, any errors on VCenter related to this VM),
what is the version of the Vmware ,VCenter ,and your Netbackup
what is the policy configuration you are using for this particular VM (Vmware tab, and advanced options inside it)
have you checked below article:
https://www.veritas.com/support/en_US/article.100024559
