Two steps I know:

1) Make sure you're on Nutaku's website (there are two of them - .com and .net so watch out) and click the "i" on the left side of the address bar. Look for flash and choose "Always allow for this site"

2) Go to "Settings > Show Advanced Settings > Content Settings... " then look for Flash.
Then click "Manage Exceptions".
Type "www.nutaku.net" or "www.nutaku.com" (depends on version you're playing 'SFW or NSFW') then choose "Allow" on the dropdown menu beside it.
Then click Done and restart your browser.

- - - Updated - - -

Forgot to mention I'm playing FKG using Chrome 57 (latest version) and the methods I've mentioned above worked for me.

No problems with my Chrome browser, did recently get some message asking to store information on computer, rejected it. Some thing about Japanese language being used. request only happens on start up, so its just another button spam to get through the loading screen. Otherwise all working as normal.

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.

I've been having the same problem, it seems that I can get the game to work like 5% of the time, and the time that it works it looks like something crashes right before it works(I can see the greyed out puzzle piece right before the game loads correctly).

Originally Posted by Discoceris

Chrome is not the problem.

You're probably using either an outdated Chrome or have changed some settings beforehand if you haven't experienced this. Check out this news. Nutaku had also warned Chrome users although I'm not seeing it now after the layout updated.

And there's no option to unblock or override Flash in your Chrome using the Control Panel in Windows. Tried it.

December 3, 2016

That's not something that would suddenly affect someone last week.

Originally Posted by Unregistered

That's not something that would suddenly affect someone last week.

I even know an entire computer cafe who haven't even updated their browser for a year. I'm also not a fan of Google Update silently working in background so months of not updating is not surprising at all. If you look around hard enough there're even users who're still using Windows XP.