What should I do if I can't download low or high level winds?

Assuming:

• your device is connected to data (i.e. you can successfully load/reload the page in Weather > Winds Aloft),
• you have Settings > User Settings > Automatic Weather Downloads turned on,
• you have winds turned on (flag icon at the bottom of the flight plan - should be white in colour),
• you haven't previously entered manual winds on this flight plan,
• your ETD is correct and it's not too far in the future (not greater than 3 days),

winds should be automatically inserted in your flight plan.

If the winds won't download automatically when the above is true, you simply need to perform an app shutdown and restart:

• Double-tap the Home button (physical button next to where the device plugs in to charge) and close (flick up) AvPlan's screenshot so it disappears off the top of the screen.
• Tap the Home button to return to your home page icons.
• Tap on the AvPlan icon again to restart the app.
• Upon app startup, leave the app to sit idle for 30 seconds or so.  The winds should be downloaded and appear in your flight plan automatically; there's no need to press the refresh/recalculate button in this case.  In fact, tapping the refresh button before the winds appear could potentially delay the wind populating.