You need to be patient when using Sdcards to flash any miner, I tried a few till I found one that works great, I don't know why but those miners are very picky about what Sdcard they like, also make sure you are copying the files in the main directory of the Sdcard, follow the steps by Bitmain very closely it should work.
Actually, it's not very picky most of the SD cards right now on the market are fake with fake volumes I have experienced this before when saving photos and videos and half of my files are corrupted that is why I end up using a tester/scanner SD card tool to know the problem and half of the total volume is fake.
I search about this issue on how to fake that volume and end up registering on a hackforum with a guide on how to make a 1GB SD card into a 2GB SD card this method is spreading and I think this is the reason why we have a fake SD card.
So only use authentic SD cards like Sandisk or Authentic Samsung SD cards. Don't buy those very cheap SD cards on the market almost all of them are fake with fake volume.