Share my location not showing my location

My son and I would like to share our locations with each other. He is able to share his location with me, in iMessage, and I can see him all the time. When I click on "Share my location" and "share indefinitely", he can never see me. It only states "location unavailable" when he clicks on the details of our iMessage. I've tried sharing my location with other iPhone users and they also cannot see me, but I can see them. If he goes to Find My iPhone and puts in my apple ID, he can see me through there. There must be a setting somewhere on my phone that is blocking him from seeing me in iMessage, but not in Find My iPhone. We both have an iPhone 6 with the latest update. Please help.