I came across this referenced in the release notes:
After upgrading NSX Manager and connecting it to an existing vCenter Server, reset the Web Client server to allow for any NSX plug-ins to be upgraded as well.
In the vCenter 6.0 appliance, you can do this by logging into the vCenter Server shell as root and running the following commands.
Command> shell.set --enabled True Command> shell localhost:~ # cd /bin localhost:~ # service-control --stop vsphere-client localhost:~ # service-control --start vsphere-client
In vCenter Server 6.0, you can do this by running the following commands.
cd C:\Program Files\VMware\vCenter Server\binservice-control --stop vsphere-clientservice-control --start vsphere-client
A restart is required to avoid unexpected errors, such as configured security groups not appearing in the Security Groups tab of Service Composer.