Updated Troubleshooting (markdown)

Troubleshooting.md

@@ -47,6 +47,7 @@ Look at the troubleshooting steps for each of the following issues:
 ### Unable to stream over the Internet
 * First, ensure you can stream successfully from your home network to ensure it's an issue specific to streaming over the Internet. If you can't, follow the instructions in the section below for general streaming issues.
 * Ensure you've forwarded the required ports [here](https://github.com/moonlight-stream/moonlight-docs/wiki/Setup-Guide#streaming-over-the-internet)
+* On your home network, go to http://canyouseeme.org/ and check port 47989 and 47984 using the tool to ensure they are both open. If they are not, your port forwarding is not configured correctly (or you have another issue, possibly listed below).
 * On your home network, go to https://whatsmyip.com/ to get your current external IP address. Use the Add PC button and type that address to ensure Moonlight has your router's current IP address (which can change periodically depending on your ISP). If your IP address changes frequently, you may look at a Dynamic DNS provider such as https://www.noip.com/ to allow you to use a hostname instead.
 * Make sure your PC's internal IP address (that you forwarded to) hasn't changed since you created the forwarding rules. If so, you may assign a static IP reservation to it via your router or a static IP address on the PC itself to prevent it from changing. Update the forwarding rules to point to the new IP address.
 * Double-check that you forwarded the UDP ports as UDP and not TCP (especially if you get the "RTSP handshake failed" error or no audio/video)