Has the VLAN been added to your ESXi vNICs in UCS Manager? If you're using a vNIC Template, add the VLAN there instead. A reboot will not be required.
Hi Trevor, I should have clarified that it has been added to the Updating Service Profile Template and it is present on the vNICS the ESXi hosts are using.
It turns out that it was not added to the trunk between the upstream switches and the core switches.