Headlights need to be on and just keep the washer/wiper stalk pressed in, they should activate after 2-3 seconds, you have to have your main headlights on, not just the sidelights.
Best bet is to do it and have a quick look at the front or get someone else to stand and watch as you do it.
If they dont work, check the fuse, as it could have blown, failing that, it will be a case of bumper off and see that its all piped up properly.
HTH