This is caused by libasound2-plugins:i386 being missing from your system. It should be installed automatically, but is not due to bug #861025.
You can manually install it by running the following command: sudo apt-get install libasound2-plugins:i386 libjack0 libjack0:i386 ** Changed in: flashplugin-nonfree (Ubuntu) Status: Confirmed => Triaged ** Changed in: flashplugin-nonfree (Ubuntu) Importance: Undecided => High -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/840826 Title: Firefox (flash) mute pulseaudio and do not appear in sound app list To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/flashplugin-nonfree/+bug/840826/+subscriptions -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs