My Photon Server Only Works On My PC

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I'm trying to make an FPS with Photon, and I used the first episode of the BlackThornProd tutorial. https://www.youtube.com/watch?v=93SkbMpWCGo Anyway, I build the game, and I test it with the build and Unity editor on the same PC. Works perfectly. I tried it on my school laptop and my PC, and it worked for a while, and then stopped working, even though I hadn't changed any code, or anything else. I send the build to my friend over itch.io, and we can't even join each other's room. Anyone have any idea as to what's wrong?