Some traffic isn't shown in mitmproxy

I am trying to capture traffic of an app. I configured a hotspot and connected the device the app is running on to it. On my pc where I set up the hotspot I use mitmproxy to capture the traffic.
To start mitmproxy I use: mitmproxy -T --host. In addition to that I redirect the traffic from port 80 and 443 to port 8080. While using this configuration I get some error saying that some malformed syntax was used in the request. There seems to be some problem with http2.
So I started to use --no-http2. That helped so now I get a valid response. But I only see traffic when I update the Inbox manually. When I send messages or get messages mitmproxy shows no traffic but in the app you can see that the message has been sent/received.
Does someone have an idea why that traffic is not shown?

Hi, the app probably uses certificate pinning.

Hope this helps :slight_smile: