I tried to reinstall the plugin:
service-control --stop vsphere-ui
rm /etc/vmware/vsphere-ui/cmCatalog/com.vmware.cis.com.vmware.nsx.ui.h5.zip
rm /etc/vmware/vsphere-ui/cmCatalog/com.vmware.cis.com.vmware.vShieldManager.zip
rm -rf /etc/vmware/vsphere-ui/vc-packages/vsphere-client-serenity/com.vmware.nsx.ui.h5-6.4.8.16724220
service-control --start vsphere-ui
Hasn't made any difference so now I think the problem is with NSX itself and not the client plugin.
