iPhone step data exists but not counted

This is messy to explain so I’ll try mostly a bullet point approach:

iPhone Health data has worked fine and been retained for many years across multiple generations of iPhone.

As of this morning, Steps totals are greatly reduced for each day going back at least a year, and that lowers W/M/Y averages accordingly.

Distance/Miles walked do NOT appear to be affected, just steps.

Under Settings/Health/Data/Apps/Health it shows “No data found”

BUT if I go into Settings/Health/Data/Devices/iPhone the Source details the correct counts are still there, they just aren’t being used on the dashboard.

I started using series 4 Apple Watch a year ago or less. For at least the most recent few months the Watch details are what I’m now seeing on the dashboard, but Watch only, ignoring iPhone data which is generally much greater (don’t always wear the watch).

Last night I activated the audio option of the Pillow sleep app, and at the same time gave that app access to my other health data, specifically including Steps I believe.

Basic laws of troubleshooting say to suspect the Pillow app, but it should have been reading steps not writing to them. But I disabled it and even deleted it and its data, but no impact on my Steps totals.

I have done multiple hard shutdowns as I’ve tinkered. The iPhone device Step data details is still visible but not used.

I have not attempted to stop it from using the watch step data for fear of losing that too.

Is there a way to force Health to recalculate totals from existing data, or some other trick to tell it to use the iPhone source data?