Nike + not syncing between apple watch and phone

If I start my run on my iPhone 7 plus on ios 11.2, it does not automatically sync to the watch. It used to work just fine. It used to be you would start the run on the phone and it would just start on the watch. If you hit start on the watch, it then starts a separate run. I have the apple watch series 2. I start the run on my phone so I can listen to music and get the voice prompts on my headphones. Does anyone know a way to get this working correctly? Am I doing something wrong?