NOT For Phantom series... I followed these instructions only to find out they don't apply to the Phantom series - specifically, the Phantom 4 Pro. Wondering now if there was a way I could have selected a DJI Go 4 folder instead of the DJI Fly folder when the step asked for permission. I've been unable to figure out a way to go back and try that.
They don't make it easy! I use a program called Android File Transfer which (if I recall) is made by google. But they keep hiding it so I can't find the link to where to download it now. There are other app out there but this one was free and works well, except on my phone where it's a bit hit or miss and I need to retry multiple times.
I assume you have logged in with your user id and password. Assuming that step wasn't missed, you do need to start the app each time you want the sync to happen - it won't happen if the app is not running. Once you start the app and wait a bit you should see a quick message pop up at the bottom telling you how many were synced. If that still isn't working then I'd suggest contacting Airdata support - they are generally pretty helpful.