I follow this question Chromium 34 and later cannot detect flash plugin
and also install pepper flash plugin by using this command sudo apt-get install pepperflashplugin-nonfree but it didn't work.
sudo update-pepperflashplugin-nonfree --install
If this doesn’t work you may need to manually configure Chromium. With Chromium fully closed/exited, run the following command in a Terminal to launch the appropriate file in a text editor:
sudo gedit /etc/chromium-browser/default
Add the following line at the end on a new line:
Save and then close. Launch Chromium and it should work.
I found this trick on omgubuntu and it worked for me.