Plex Not Updating

Hi,

I installed plex using the following code.

wget -O - http://shell.ninthgate.se/packages/shell.ninthgate.se.gpg.key | sudo apt-key add -
echo "deb http://shell.ninthgate.se/packages/debian jessie main" | sudo tee -a /etc/apt/sources.list.d/plex.list
sudo apt update
sudo apt install plexmediaserver -y

And now I see the first update since installing, yet its asking me to manually update. I check my Lubuntu 16.04.1 system for updates, and there are none for Plex. How am I supposed to update?