What is the file name of the Flash Player installer you are using?
Flash Player requires Administrator permissions to install. Please ensure that your user ID has sufficient permissions to install Flash Player.
If you do, please see Where do I find the Flash Player installation log on the Macintosh? and provide all install log files mentioned in the FAQ.
Some weeks ago I started having the same problem with non-installation of Flash Player on my Macbook Pro OS X 10.10.3. Never had a problem before and the environment hasn't changed.
I have also uninstalled FP and tried again to install, without luck. I am a full administrator (and only user of this computer).
I located the installation log and followed the instructions re. placing a marker and running the installer. However, the installer returns with the insufficient permissions message and no, repeat, no entries follow below the marker. Nothing changes. Any help / suggestions will be gratefully received.
Please provide all four files listed in the FAQ Where do I find the Flash Player installation log on the Macintosh? The FAQ contains instructions to upload the files. Please post the URL to the files in your reply.