Note I've seen a lot of client related issues while lurking on the forum and scrolling through the chat. Like most new players, I had my share of client issues when I began my Runex journey a few months ago. It'd suck if new/old players like you have to leave because you can't even start the game. The client issue guides posted by Jean Paul and Ryan are detailed and should fix most problems, but sometimes the computer requires some help to run the jar files. If you have tried the other guides and the client refuses to run, then you are likely to find your answer here.  Requirements Updated java 8 and jdk 8  Runex jar file  Solutions Step 1: Open command prompt or terminal and cd to the location of your runex jar file.  Example. cd Desktop Step 2: Copy and paste  "java -runex.jar"  (without quotations) into the next line. Bonus solution: If your computer is unable to associate jar files with java, then try a program like Jarfix (this fixed my client issue).   Best of luck, I hope to see you guys in-game.