Ok, so, I installed Ubuntu-Restricted-Extras on Ubuntu version 16.04 LTS. I have all the updates. I used the terminal to install it because I couldn't find it in Ubuntu Software. But what I want to know is the Ubuntu Software Center, is Ubuntu Software and Ubuntu Software Center the same thing? Because if they are there is something wrong with mine, I can't install things like preload at all and flash player won't work (has it been removed?). In the Ubuntu Software app there are hardly any programs, and again, nothing like preload or Ubuntu restricted extras. Help me I am going bloody insane.
I don't think Ubuntu Restricted Extras Won't Work.
I think the problem is 'Ubuntu Software [Center]'. Maybe the following link (within AskUbuntu) can help you solve that problem.
But there are work-arounds.
Continue to use the command line tools,
to keep Ubuntu up to date
sudo apt update sudo apt full-upgrade
to keep Ubuntu clean (remove unnecessary program packages)
sudo apt autoremove sudo apt autoclean sudo apt clean
to install a new program package
sudo apt install program-package
Use the Synaptic Package Manager
sudo apt install synaptic
and start it from 'Dash', after clicking on the Ubuntu icon at the top left corner and typing
There is a learning curve, but Synaptic is reliable and powerful. Later on, when 'Ubuntu Software' starts working again, you might stay with Synaptic, because you know it and like it :-)