Chrome is not the problem.

1. Clear cache. In the upper right hand corner, look for the 3 dots, and click on it, and click on More Tools > Clear Browsing data

Failure to do this, and I know many people don't do this or for some reason resist doing this, will keep the game from running.

2. In Windows, no matter what version you're running, go to Control Panel and find Flash Player (in Windows 10, in upper right corner of control panel, change from Category to one of the sized icons) Change the settings here (see the above posts) as it will be GLOBAL (prevents Chrome from interfering with the settings)

3. Reminder for Chrome (Windows) - personal settings, such as sound levels for the game, as well as UI options, will always reset after a Nutaku update. In my case, the speed toggle for battles always default to off whenever I close Chrome, but that's about the only annoyance I have come across.