Blackberry won't go on Internet?

I bought my daughter a blackberry for her birthday. It's second hand and in very good condition. I've no reason to suspect there's something wrong with it. We just can't get it to go online. It's set up to my Internet. It's hooked up to router and has full bars. It just won't connect. It says Internet wont connect or something and please try later. Is there something we're not doing right.