I personally can't recommend using the browser Flash plugins (Chrome/Firefox) anymore, it can be risky for your computer from now on. It's still in development and we will expect big changes on v2!
📢 I made Flash Forwarder Tools, an alternative to NG Flash Player for those who can't get Flash work! For Windows and MacOS. I'll eventually finish that project because we still don't have a solution for not Windows users! Check Flash Forwarder Tools if still doesn't work. If does not work, try using Internet Explorer without uninstalling it. 📢 Newgrounds Player 1.0.7 is now out! Should fix most of problems in this guide.