The Privia client is built on the Microsoft .NET framework and cannot be run on a MAC or non-windows machine.  The core features of Privia can be accessed through a Web browser using Internet Explorer, Firefox, or Safari.  

Near the bottom of the Privia invitation page is a link to access Privia through a Web only client. Click on the link in the invitation and scroll to the bottom of the page to get the link to log onto the Privia server.  Each server address is unique so you will need to follow the link in the invitation.  Bookmark the link to avoid having to go to the invitation every time you want to log in.  

When you are prompted for the credentials provided in the invitation as follows:

Username: PRIVIASERVER\username

Password: PASSWORD