Having the Same issue for three days now and have tried every suggested method to try and fix and no results. Macbook Pro 10.10.2
Please try the offline installer posted at the bottom of the Installation problems | Flash Player | Mac page in the 'Still having problems' section.
Please also try the offline installer. If that doesn't work, please provide the FlashInstallManager.log file saved at /Users/YourUserID/Libarary/Logs using the instructions here The specified item was not found.
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