I'll need to get some installation log files from you to troubleshoot further. Please review the FAQ Where do I find the Flash Player installation log on the Macintosh? and configure your system to obtain all four files listed: Adobe_ADM.log, Adobe_GDE.log, install.log, and FlashPlayerInstallManager.log. Run the installer again. When the installation fails, gather all files and upload them to cloud.acrobat.com/send using the instructions at How to share a document. Post the link to the uploaded files in your reply.