If you're getting a network error and none of the suggestions in the article are helping fix it, you can still try to use ZeroTier, a P2P VPN. Both the person hosting and the people joining will need to set this up on their machine. This is a bit of a nuclear option, and it may add a lot of latency to the connection or not work, but it's relatively easy to set up and worth trying.
- Download ZeroTier on both devices
- One of you (preferably the host) should go to ZeroTier Central and click "Create a network". You'll need to create a ZeroTier account to do so
- Once the network is made, it'll show under the yellow button. Click the network to open its settings
- You can copy the ID of your network from here. You and your friend will be using it to join
- On both devices, click the ZeroTier icon in the taskbar and click "Join Network..."
- Paste the network ID and click Join
- Once both devices have joined, go back to the network's settings in the site and approve both the devices in the Members section
- At this point, Parsec may already work. If it doesn't, you both may also need to set ZeroTier to the highest priority on Windows. Press Windows key + R, type control netconnections, and press OK
- Right-click ZeroTier, click Properties, then Internet Protocol Version 4, then Advanced
- Disable Automatic metric
- Set Interface metric to 1
- Click OK on every single window to apply the settings
- Once done, repeat these steps for the non-ZeroTier networks available in the list, except set the Interface metric to a number bigger than 1. Make sure to click OK on every single window to apply the settings
At this point, Parsec should work properly, and you can try to connect to each other. If you still have trouble connecting, you both should check if the Interface metric is still applied correctly on all the networks, and that ZeroTier has a lower number than everything else. Also make sure that ZeroTier is still running on both devices.