As flash is end of life and end of support in 2021 many of you are not able to use the vSphere web client flash-based.
I still have some of my vCenter servers on 6.5 which support the VMware HTML5 web client however to manage some of my NSX 6.3.x task is not supported on it.
I have manged to run vSphere client on my chrome and internet explorer as workaround and below are the steps you need to perform.
https://kb.vmware.com/s/article/78589
To work this successful you need to make sure that you still have flash installed on your system
Internet explorer is using flash installed on system.
Chrome has its own flash installed in another location.
Check out the dates in the screenshot.