To force Apple Watch to sync with your iPhone, you have to reset sync data. But before you get there, see if all connections between the Apple Watch and iPhone are enabled.

Open the Control Center on your iPhone by swiping down from the top-right corner of the screen. If you have an older iPhone with a Home button, swipe up from the bottom of the screen.

Here, in the “Toggles” menu, make sure the “Bluetooth” and “Wi-Fi” toggles are enabled.

If your Apple Watch still isn’t syncing, you can use the force sync method.

Open the “Watch” app on your iPhone. Use Apple’s built-in Spotlight Search if you can’t find the app on your smartphone. Next, from the “My Watch” tab, select the “General” option.

From here, swipe down to the bottom of the page and tap on the “Reset” option.

In the new menu, tap on the “Reset Sync Data” button.

Your iPhone will now erase all contacts and calendar data on your Apple Watch, along with sync settings. Once the process is complete, it will start the sync process over, this time syncing all the data from the Apple Watch to your iPhone (and vice-versa). This should fix your health and activity data sync issues in addition to any problem you might be having with third-party apps.

If you’re still facing sync issues, the last resort is to unpair and repair the Apple Watch.