more update, I finally managed to get my mitmproxy-ca-cert.p12 in my C:\ directory. I launched the command, but I still get the same error message above. Alternatively, I used the "Windows certificate import wizard" to import this certificate.
After I imported the certificate, I re-run the mitmweb and monitor my traffics. I configured my firefox via the proxy (Mitmproxy) to access the Internet.
However, I only observed the http traffics from my mitmweb. No https traffics have been captured.
Any ideas why this does happen? Did I miss something configuration?