Installing adobe-flashplugin on Ubuntu 16.10 for Firefox

Solution 1:

Add this line to /etc/apt/sources.list:

deb http://archive.canonical.com/ubuntu yakkety partner

and run

sudo apt update

Solution 2:

It seems that you are pulling from an old repository.

Go to Software & Updates>Other software.

Then remove the old repository called:

http://archive.canonical.com/ubuntu maverick partner

Then enable the 'Canonical Partners' repository.

If it doesn't exist, click add and type in:

deb http://archive.canonical.com/ubuntu yakkety partner

Next, run:

sudo apt-get install adobe-flashplugin

Flash Player should now be installed. Restart your browser for changes to take effect.