Urinary i/o cath difficulty

OK so I've floated last week and again this week. I am assigned a 8yr old male spina bifida pt in for IV abx. He's ordered to be i/o cathed Q4. Both times, once last week, and once this week, I get no urine out. I'm using a 10F which the day nurse used with result. I haven't cathed many pts. Am I just not going far enough? Obviously, I don't want to cause trauma so I'm not going to force the cath in. I am a traveller and the floor I'm on isn't all that friendly so I'm really hesitant to ask for help. Any ideas? Looking at his chart he's been successfully cathed in the past. Don't know what I'm doing wrong.... I can feel the cath in the scrotum and it's not stright in. It's got a bend in it although it's not looping.