Have you tried turning off Protected Mode yet?
The only stable 64-bit Flash experience on Windows 8 came via Google Chrome . Google got fed up with Adobe’s slow 64-bit progress. They forked Flash into "Pepper API" (PPAPI), sandboxed it, and shipped a 64-bit version inside Chrome. If you used Internet Explorer 10 (the default on Win8), you were stuck with 32-bit Flash. If you used Firefox 64-bit (which barely existed), you were out of luck. adobe flash player 64 bit windows 8
Do not download "Flash Player" installers from third-party websites. Since Adobe killed the official download links, malicious actors have flooded the internet with fake "Flash Updaters" that actually install viruses on your Windows 8 machine. Have you tried turning off Protected Mode yet
The Ghost in the Machine: Revisiting Adobe Flash Player 64-bit on Windows 8 They forked Flash into "Pepper API" (PPAPI), sandboxed