I have an Android phone, and I have to resync it with my Google Fit all the time. I think it auto-desyncs when my phone gets low battery, which is often these days.
And to link your iPhone with Apple HealthKit, more helpful instructs with screenshots: https://help.onedrop.today/support/solutions/articles/19000055370-apple-healthkit … If you have any trouble getting set up, feel free to reach out at customerservice@onedrop.today!
In your One Drop app, go to Settings > Reports > Pick your report! Here’s a helpful step-by-step: