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Functionality Updates for the vSphere Client
Try with another browsers .. Delete your cookies (if you can) and check the URL again
Check the proxy settings in your client system
Is there any other self-signed certificate related to your vCenter server?
the problem was solved by https://www.altaro.com/vmware/customize-vcenter-sso-login-page/
- unpentry.jsp file.
My new logon screen: phptp from our national park 🙂