I've followed the steps in the tutorial and my server was working fine last week. I had set up port forwarding rules so that my friend from outside my wifi network was able to connect to it. However, today the server isn't working properly. I can still connect to it from localhost, but my friend can't connect to it using my external IPV4 (which he could last week). I checked to make sure that my external IP has remained the same (because I have a dynamic IP address) but nothing's changed. The internal IP for my computer has remained the same because I have a static internal IP address, but I checked anyways and everything looked like it should be working. I checked to see if my port was open, but it was not. (According to this website). I haven't changed anything, what could the problem be?