E: Unable to locate package parrot-sphinx on Ubuntu 18.04.5 LTS

Hi, I tried installing Sphinx by following the instruction in the documentation
executed the following commands:

$ echo “deb http://plf.parrot.com/sphinx/binary lsb_release -cs/” | sudo tee /etc/apt/sources.list.d/sphinx.list > /dev/null
$ sudo apt-key adv --keyserver keyserver.ubuntu.com --recv-keys 508B1AE5
$ sudo apt update
$ sudo apt install parrot-sphinx

Reading package lists… Done
Building dependency tree
Reading state information… Done
E: Unable to locate package parrot-sphinx

I am able to see sphinx.list file got written in the /etc/apt/sources.list.d/ correctly

Any hints are welcome.

Thanks in advance.

Wei