Cannot start intercepting traffic in windows 10

I installed mitmproxy for windows and installed the certificate (with a blank password). I ran the mitmproxy ui and it opened up in chrome. After this, I visited http://mitm.it/ and got this message “If you can see this, traffic is not passing through mitmproxy.” I was expecting mitmproxy would start intercepting traffic, but it does not. How do setup mitmproxy and start intercepting http traffic ?

Thanks !