I had problems getting to sleep when I was a child. Looking back I never felt tired when I went to bed - it’s very hard to fall asleep if you’re not tired. I was not allowed to read in bed so I just lay there thinking! Why don’t you try moving his bedtime to an hour later? Stop him looking at screens for a couple of hours before and give him a book to read. Make sure his room is really dark. If he still finds it hard then you could maybe try him with an app such as Calm which reads really boring bedtime stories! Good luck!