I have download Yosemite on my MBP and created a Bootable USB Installation to allow me to install Yosemite on my Mac Server too, I've used Disk Utility and erased the partition and went to install Yosemite on my Mac Server but i keep getting this problem. I choose which drive i want Yosemite to be installed on, I then get prompted with Sign in to download from the App Store. When i sign in with my Apple ID and Password i get this message 'This item is temporarily unavailable. Try again later.' This has been happening all day and i'm left with a Server with no OS installed. Any Ideas?