Unable to Add Virtual Machine Name - VMware

We have two data centers, each with their own vCenter server, we'll call them vCenter A and vCenter B. 
We also have two Netbackup 5230 Appliances at each location, we'll call them NBU A and NBU B.

I'm trying to add a Virtual Machine Names to Netbackup to perform VM level backups. NBU A can add vCenter A and B credentials without issue. NBU B times out when trying to add either. 

The exact error is "The operation timed out. The operation has exceeded the time out limit, though the service or daemon may still be processing the request. (195)"

We are using the same username/password for everything. It doesn't matter what credentials I use, a correct one or made up, both time out. From NBU B I'm able to ping and trace route both vCenter servers by both FDQN, shortname, and IP address. DNS, Gateway, and Hosts entries look identical on NBU A and B. 

Running each of these commands from each NBU appliance shows the same results. 
w3m https://<vCenter_name>/sdk
openssl s_client -connect <vCenter_name>:443
telnet <vCenter_name> 443

Properties of both Master Servers look the same. Same servers listed under Servers. Same servers listed until VMware Access Hosts. I've tried rebooting the NBU appliance several times. The only difference I can tell is that NBU A is running 7.7.3 and NBU B is running 7.7.2, but I can't imagine that's the cause. Anyone have any suggestions for me?

Thanks in advance!