In order to to capture the HTTP/HTTPS message in iOS devices, please navigate to:
Certificate Menu -> Install Certificate on iOS Simulator
The following photo describes thee steps:
Install Root Proxyman Certificate on your machine: You can follow the macOS Guide.
Install Proxyman Certificate to available simulators, which you have opened at least one time.
3. Reset the simulators: Proxyman tries to reset all simulator, and it will load new Certificate.
After the installation, we can start capture and view HTTPS message by following SSL Proxying Doc