Hello
While following the kb mentioned, did you find multiple entry for the webclient under the below directory:
Virtual Appliance:
/etc/vmware/vsphere-ui/vc-packages/vsphere-client-serenity/
/etc/vmware/vsphere-client/vc-packages/vsphere-client-serenity/
Windows:
C:\ProgramData\VMware\vCenterServer\cfg\vsphere-ui\vc-packages\vsphere-client-serenity\
C:\ProgramData\VMware\vCenterServer\cfg\vsphere-client\vc-packages\vsphere-client-serenity\
if you do remove both and re-attempt the registry, make sure to refollow the steps before and in between.
Thanks