Watching chicks when you first open the pop door can be a lot of fun. With some broods every chick is on the ground within 15 minutes. With some broods it might be three days before the first one ventures out, but it is hilarious watching them at the door looking out for those three days. Some chicks are not very trusting. What’s more normal, if anything can be called normal, is that it takes several hours, maybe overnight, but eventually one ventures out. Sometimes it hops right back in, sometimes the rest follow if it stays out a couple of minutes. Sometimes a few follow it out but the rest still wait a while.
Just be patient. They will venture out when they are ready.