Repair/Format corrupted SD card

[Kerlingen]

Quick way:
Overwrite sector 0 of the SD card (physical sector 0, not partition sector 0), remove it, then insert it again into the reader. When accessing it Windows should complain something about that the disk has not been initialized and asks you if you want to do it and format the disk afterwards.

However if normal format gives an error, the SD might be physically damaged. It's nothing which you could see with your eyes, it might be something as simple as too many writes to the sector storing the root directory and now all further writes will fail.

Or you might have a cheap 10 TB eBay fake SD card which is only a few GB big and ROM.

Generally: If it's a big expensive card with warranty send it back to the manufacturer, else throw it away and buy a new one, these things don't cost much and if a card becomes unreadable once there's a high probability it will happen again soon.