What operating system and browser are you using? I'll assume you are using a Mac, in which case can you please try this installer instead?
It does work on my macbook pro
This morning we resolved a problem that prevented Flash Player installations from completing for some of our Macintosh users.
If you encountered this problem, please delete any previously downloaded Flash Player installer and either:
1.) Download the installer again from https://get.adobe.com/flashplayer
2.) Download the stand-alone installer from http://fpdownload.macromedia.com/pub/flashplayer/latest/help/install_flash_player_osx.dmg