Apple Watch and iPhone sync

hi

for ref purposes: I have latest (aug 2019) Apple Watch and latest iPhone XR both using the latest os releases .

My question relates to when I forget to wear my watch .happens occasionally when I leave before dawn with the dog for a run . The iPhone does not appear to measure my steps or activity . It did previously with earlier versions of the Apple Watch and iPhone . Is there something in settings that is not configured right ? The Apple Watch has its own cellular .