To install flash player , try using Pepper Flash Player for Chromium.
Install as per following steps.
1> To add the PPA and install Adobe Pepper Flash from Google Chrome in Ubuntu
sudo add-apt-repository ppa:skunk/pepper-flash
sudo apt-get update
sudo apt-get install pepflashplugin-installer
2> you need to open /etc/chromium-browser/default as root, for root (open in any editor e.g.:- nano or gedit)
sudo -i
gedit /etc/chromium-browser/default
or
nano /etc/chromium-browser/default
paste the following line at the bottom of the file (after the CHROMIUM_FLAGS="" line):
. /usr/lib/pepflashplugin-installer/pepflashplayer.sh
Note:- there's a dot in the beginning of the line, then a space!
3> Restart Chromium browser & visit chrome://plugins. you will notice Adobe Flash Player of latest version.