Get stuck here:
sudo apt-get install python-certbot-nginx
Reading package lists… Done
Building dependency tree
Reading state information… Done
E: Unable to locate package python-certbot-nginx
Have done some more research concurrently while waiting for feedback from the hosting company.
Additional actions I have taken are:
Edited: /etc/apt/sources.lst.
Now with the following information:
deb cdrom:[Ubuntu 16.04 LTS Xenial Xerus - Release amd64 (20160420.1)]/ xenial main restricted
deb Index of /ubuntu xenial main restricted universe multiverse
deb-src Index of /ubuntu xenial main restricted universe multiverse
deb Index of /ubuntu xenial-updates main restricted universe multiverse
deb-src Index of /ubuntu xenial-updates main restricted universe multiverse
deb Index of /ubuntu xenial-backports main restricted universe multiverse
deb-src Index of /ubuntu xenial-backports main restricted universe multiverse
deb Index of /ubuntu xenial-security main restricted universe multiverse
deb-src Index of /ubuntu xenial-security main restricted universe multiverse
deb Index of /ubuntu xenial-proposed main restricted universe multiverse