I can see the video files on my phone. However, when I plug it into a computer, mac or pc, the video files are missing; but they do say the card is full. I'd download directly to my phone, but they're 4k. A reshoot is not really an option in this case.

Do you mean you plug your osmo(sd card inside) to the computer ?

Try using a sd card reader remove the sd card from the osmo hmm

Arcobaleno Reborn Posted at 2018-3-16 10:56
Do you mean you plug your osmo(sd card inside) to the computer ?

Try using a sd card reader remove the sd card from the osmo hmm

I've done both

I found that, when I delete a file from my sd card while in my computer, it stays in the trash.  I have to empty the trash - while the card is still plugged in - to clear that from the card too.  Hope that's what you're finding.  My fix was simple to clear it from being a problem for me.  

Please ensure that your SD card has enough space before shooting. Are you using OSMO? You can save the cache video from your phone. Here is the path:  
DJI/dji.pilot/DJI_RECORD (Android device)
DJI GO/Documents/videoCache( IOS device)