Hi Jonathan. Host is displaying proper value for both host and client. Client is messing text value., also is not updating points from host. Any clue, looked at script and everything is ok, maybe UNet is obsolete ?
Unfortunately Unet is obsolete by now so I'm not sure how much you'll gain by learning it now. They are coming out with a new Unity Networking system this year I believe.
As far as the issue you're having, you have to make sure that when one player collects a cookie that the method associated with that is called for everyone. When I was testing it, I played as the client first to see if it worked, then tested it as the host. It's a bit of a tedious process. Playing as the client lets you know if it's working in a multiplayer environment while playing as the host gives you options to debug with the console.