Flash Player suddenly stopped working on Macbook Pro OS X 10.10.1

Flash Player suddenly stopped working on my Macbook Pro running OS X 10.10.1 and Safari 8.0.2. I am getting this message in the language learning program I have been using successfully for 6 months:

"We can't play Sound in your browser

It's possible that you have browser extensions that block Flash or that Flash crashed.

Let's fix this! If you have a Flash blocker add 'duolingo.com' to its whitelist. If Flash crashed try reloading the page.

Sound still not working? Go to the settings page in the top right corner to disable the speaker."

Reloading the page doesn't work. Restarting my computer doesn't work. I don't know if there is a Flash blocker on my system. In System Preferences, Flash Player I have set this program (Duolingo) to "Allow" for Camera and Microphone access. Any suggestions?