try deleting and reinstalling
I have the same issue on Linux with a fedora with google chrome browser. I've had problems for a while, could only get it to work by disabling the sandbox but even that doesn't work now. Reinstalling does nothing.
There's not enough information here to really give you an answer. The content provider built a large, complex application on top of ActionScript. Flash Player is a language runtime. We're interpreting the bytecode in the compiled application and doing the low-level stuff like allocating memory and drawing pixels (and with 3D content, we're largely just handing that off to the 3D graphics drivers).
We're not going to debug someone else's large complex application. The game developers are best positioned to do that. In the unlikely event that they find a language-level problem with the Flash runtime, they'll have a detailed technical analysis about a given API call that doesn't work. That's the kind of problem that we can actually do something about.
That said, a couple observations:
Your best bet at this point is to talk to the game developer. They're in the best position to debug the problem and understand why it's failing. They can then either fix it (which seems the most likely outcome), or they can give us a very precise description of what's not working in Linux at the language level, which is really what we need.