If you have been pulling your hair out trying to figure out why real-time aircraft is not appearing in Microsoft Flight Simulator 2020 then this may be for you.
Like many, I downloaded the simulation and setup my experience, and enabled Real-Time Aircraft in Microsoft Flight Simulator 2020 - but after several days of flying the sky was bare and lifeless. I tried unchecking and re-checking the box in General settings "traffic" but nothing changed. I tried AI Aircraft and that worked but not real-life aircraft.
The issue is in your network settings at your router level you need to open ports. I can only share my setting for users with a PC, below are the ports I opened to get live aircraft.
-- In particular, you need to open Ports 30100 - 30102. Below are my ports I opened for Microsoft Flight Simulator 2020;
Ports for the Steam Edition:
Open Ports for Steam Edition
Ports for the PC Edition:
Open Ports for PC Edition
If you need assistance on the technical procedure for your router use this link to find your router and port forwarding information: https://portforward.com/router.htm
I use a high-End Firewall "WatchGuard" so I set up two firewall policies to allow those ports and now I have real-time aircraft and also better framerates.
I hope my advice helps solve the missing live aircraft issue in Microsoft Flight Simulator 2020 - it did for me!