We need more info. Are you hooking it up wirelessly? Hardwired? What type of error message if any are you getting?
Do other devices work fine wirelessly/hardwired.
If you've tried both hardwired and wireless and other devices work fine with both then it's most likely a hardware issue with your ps3... A quick way of testing that is to connect to a different network at a friends or something.
More info and we may be able to help you sort the issue out.