When you hook up an external storage device (such as an external hard drive, your GoPro, etc) to your Mac, and delete files from it when it’s connected to the Mac, you need to empty your trash before removing the device from the Mac. Otherwise, it wont show those files are there, but they”ll actually still on there taking up space… Pretty lame Mac thing IMO, but can’t hose you once you know about it.
Another option, go into the settings menu on your GoPro, click the power/mode button until you see "ALL" displayed, and then press the shutter button a twice (once to select delete all and the second to confirm it). That will delete all the files from the SD card and I’m pretty sure it reformats the SD card as well. Hope this helps.
thanks man its finally working! trail time 😃