Open your Android Emulator -> Setting app -> Wifi: Make sure your Wifi connection is good. Sometimes, it's "Limited Connection" that you could not set the Wifi Proxy. If it happens, please remove the emulator and create a new one again.
Click on the Wifi then clicking on Edit Button in two places
Start set HTTP Proxy that the same IP and Port value from Android Guideline (Proxyman app -> Certificate -> Install Certificate on Android Devices)
Make sure the Proxy Hostname and Port match with the values in (Proxyman app -> Certificate -> Install Certificate on Android Devices)