Apple watch usage not syncing across devices with screen time

I have followed all the suggested steps to set up screen time on my child's apple watch. (He has an iPad, but no phone. Screen time syncs accurately with his iPad.) When I follow the suggested steps to click family watches, my child's watch, screen time - the section says "Screen time is where you go to manage parental controls....", gives me the option to go to screen time settings, but is otherwise blank. When I go to screen time settings, the only device listed is his iPad. The watch does go into Downtime at the correct time, but doesn't turn off iMessage when his messaging time limit is up. He does not have messages "always allowed".