I had an annoying issue in my lab. Some time ago when I performed vSphere 6.7 PSC convergence my vCenter would stop displaying proper names of tasks in the vSphere Clients UI (both Flex and H5) and show only their placeholders with names like xxx.label.
While there are some KB or communities articles about the issue (and fix) none of them was applicable to my situation (running vCenter Server 6.7U1). I thought that VCSA patches or even deploying new appliance with backup restore would fix it but it did not.
After a little research I found out that the issue is caused by missing catalog.zip file in the /etc/vmware-vpx/locale/ folder. I had another lab with the exactly same vCenter Server build deployed so I just copied that file and transferred it to my vCenter Server Appliance. After service restart via VAMI UI tasks names were back.
I do not know the root cause, but if you have the same issue, give it a go.