So here is the problem. I have a server of my own and there is a plugin that I made on it. My friend also has a server, and we wanted to put my plugin on his server, so I copied the .jar file for my plugin and sent it to him. He put the .jar file into the plugins folder of his server and restarted the server. Unfortunately, when we logged onto the server, the plugin wasn't there. Now I know the plugin works because it worked on my server, and I know his server can have plugins because there are other plugins on it that do work, so I don't know what the problem is. I don't know if this is important but I'm on MacOS and he is on Windows10. If anyone could help, that would be great.