Probably too much light pollution. Unless you're far away from any light it's difficult to see with the naked eye. Try taking a picture with a long exposure (just a couple seconds should do it). You'll want to be looking North and they can change in intensity through the night but I was able to get some good photos around 11:30.
After it started getting dark. It was very vivid around 10:30ish to 11:30 or so. I went to sleep after that though, so it might've gotten brighter. I was checking periodically earlier but wasn't seeing anything til it suddenly became visible.
