If, after recording an activity on the iOS app, you are unable to sync the activity give the following a try:
- Log out and then back into the Strava app.
- Turn your phone off and then back on again
- Make sure you are in an area with good data coverage or, even better, connect via WiFi and pull down on the 'You' feed slightly (but not all the way) as if you were going to refresh. Your phone may tell you that you have Pending Uploads at your Feed (highlighted below). From here you can tap the Retry button to prompt your phone to attempt the sync again.
- If this doesn't work, the activity may be corrupt and will be unable to upload. In this case, you'll need to remove the failed upload. Tap Pending Upload to navigate back to the 'Unsynced Activities' page and tap Delete.