Some users who complete an activity in Watch Only mode and follow the correct procedures to save an activity, discover that upon opening the Runkeeper Phone app their activity hasn't synced.
The activity does seem to be displayed in the Apple Activity App, but for some reason won't display in the Runkeeper app.
One potential workaround to get those activities to resync, is to open the Runkeeper app on the phone as well as on the watch. Then, force close the watch app, re-open the watch app, and then refresh the activity list in the phone app. If the activity still doesn't appear, try logging out and back into the phone app, that might just do the trick.
Important Note: Always double check that the phone and watch are connected via Bluetooth when syncing.
If the activity still hasn't synced over after those workarounds, reach out to Support and we'll make sure you're updated once this bug is fixed!