The following steps may help:
If you have not yet done so, update your iPhone and Apple Watch to the latest compatible software versions, starting with your iPhone:
On your iPhone, in the Watch app, to go: My Watch (tab) > Health.
- Close the Watch app, Activity app and Health app (if open) on your iPhone:
- Double-click the Home button, then swipe up on each app preview to close the apps.
- Turn both devices off together, then restart your iPhone first:
If missing achievements are not credited in the Activity app immediately after following these steps, wait until the next day to see whether they are instead credited then.