It could be VLAN settings. Each host comes pre-configured with vmnic0 with no VLAN setting. The VxRail Manager VM uses the Management Network and the VM Network that are pre-configured by default, both with no VLAN.
You can change VLAN settings for the host itself in DCUI (the main console) , then go into network settings and set the VLAN there. The trick is you then need to login to the host via SSH and set the VLAN for the VM portgroups. One way to do this is to set a temporary management IP on the host, set the VLAN, enable SSH in the troubleshooting section of DCUI, then login to the host via SSH. Change the VLAN settings with the following:
esxcfg-vswitch -p "Management Network" -v <VLAN ID> vSwitch0
esxcfg-vswitch -p "VM Network" -v <VLAN ID> vSwitch0
Also, if you want to change the VxRail manager IP address, you can do so by following the directions in the following article:
490026 : VxRail: Customizing the VxRail Initial IP Address https://support.emc.com/kb/490026