I am trying to add a new Hyper-V server to my server cluster but when I enter my server IP address it says "Error: Unable to connect. Please verify HC Provisioning Service is running properly on remote server."

What does this mean?

To add any server into your HC10 Panel you have to install HC agent on that server. You can download the latest HC10 agent from the following link: https://hostingcontroller.com/Hosting-Software-Downloads/HC-Service-Packs.html.
 
There are two types of HC installers, the Primary Installer is for the HC master server and HC agent Installer is for the remote server that you would like to connect with your HC master server.