There are quite a few problems that could lead to you getting that message. In order of easiest to hardest to fix, here's a few of them:
1: It could be that your PS3 is not connected to the internet.
- Try going to the browser on the Playstation, and try loading a basic webpage, like www.google.com. If that works, then try Netflix again.
- If you're not connected to the internet, then go back to the main menu, and go to the internet (or maybe it's called network, not sure) settings. Sign in to your home or dorm's wireless network, if there is one. I can't help you with that, as each network is different.
- If you cannot connect to a wireless network, or if one is not present, then try connecting your PS3 to the internet using an ethernet cord, if you have one. (It looks like a phone cord, but the ends are bigger.)
2: If you are connected to the internet, and you still can't access Netflix, then there's a few more things to try.
- Most easily, turn your Ps3 off then on again. I'm not super sure if that will fix it, but it can't hurt to try.
- Make sure that you're using the correct username/password to sign in to the Playstation Network, and that you're using the right combo for Netflix.
3: If none of those work, then there could be a deeper network problem. Perhaps your home internet is set up incorrectly, or maybe Sony or Netflix are having server problems. Whatever the reason, I can't help beyond this.