In Chrome go to https:\vmware-plugin:8094 and click advanced, proceed. This will approve the certificate for the plugin.

Go back to vCenter and log in using enhanced authentication.

This happens from time to time when Chrome loses the trust of the certificate after clearing cookies, cache, etc.

Yeah, except the "Proceed" button no longer appears... The plugin sends back 'unusual and invalid credentials'. 

Clear cache and cookies. 

That is not the issue. The certificate for the plugin is no longer trusted due to a change in the Chrome browser. This is a known issue. It works with the Edge browser. 

Testing this is easy: when you try the same in a Chrome Incognito window the issue also appears, which rules out cache and cookie issues.

so edge only?

will it be fixed in later versions?

Currently Edge only (from what I have tested). The issue already presented in FireFox in earlier versions, now also in Chrome. Not sure if it will be fixed in future versions...

Edge and Firefox works

It also works in Chrome, but you have to use a small workaround. On the screen with the certificate error in Chrome type "thisisunsafe" (without the "" and without clicking anywhere.) This will bypass the certificate error and after that the plug-in works once again. This also works in other Chromium Browsers.

Apparently this workaround is no longer necessary. I think Google fixed this issue in Chrome 111, since all my systems now again accept the plugin...