apt - Ubuntu 16.04 cannot locate Skype after enabling Canonical Partners in Software & Update

I am experiencing this problem for the first time with Ubuntu 16.04, after a fresh installation.

Skype cannot be located after enabling Canonical Partners both in Software & Update, or by command line with the command:

sudo add-apt-repository "deb http://archive.canonical.com/   $(lsb_release -sc) partner"

Then running the following:

sudo apt-get update 
sudo apt-get install skype

However, I still get:

E: Unable to locate package skype

Any clue?

UPDATE

I run "sudo apt-get update --fix-missing" before trying to install skype, and this is the output I get:

Hit:1 http://cran.rstudio.com/bin/linux/ubuntu xenial/ InRelease

Hit:2 http://archive.canonical.com/ubuntu xenial InRelease                                                                                   
Hit:3 http://id.archive.ubuntu.com/ubuntu xenial InRelease               
Get:4 http://security.ubuntu.com/ubuntu xenial-security InRelease [102 kB]
Get:5 http://id.archive.ubuntu.com/ubuntu xenial-updates InRelease [102 kB]
Get:6 http://id.archive.ubuntu.com/ubuntu xenial-backports InRelease [102 kB]
Fetched 306 kB in 3s (79.5 kB/s)  
Reading package lists... Done

I try "sudo apt-get install skype" again, and I obtain:

Reading package lists... Done
Building dependency tree       
Reading state information... Done
E: Unable to locate package skype