Facing Error with Custom Server Certificate generated locally using openssl commands

[Srijan67]

I followed this docs link in mitmproxy: https://docs.mitmproxy.org/stable/concepts-certificates/#using-a-custom-server-certificate
where i generated my cert.crt, cert.key and cert.pem using the command. I then added crt to trusted root ca (since i am using windows platform and pem was not supported on import).
on hitting command mitmdump --ssl-insecure --certs *=cert.pem I am getting error: "Client TLS handshake failed. The client does not trust the proxy's certificate for ssl.gstatic.com (OpenSSL Error([('SSL routines', '', 'sslv3 alert certificate unknown')]))". why so? and how to make it work.

mitmdump version Details are :
Mitmproxy: 10.2.2
Python: 3.12.2
OpenSSL: OpenSSL 3.1.4 24 Oct 2023
Platform: Windows-11-10.0.22621-SP0

Please , Let me know what I am missing here.