To determine if the card is a fake, use a tool like H2testw. It writes data to every sector to verify the actual usable capacity against the advertised size.
: This error is a known hallmark of counterfeit or "fake" SD cards that use hacked firmware to misreport their actual storage size. How to Resolve SD Card Corruption
[PGv1] SD card stopped working? NOT missing CFW! : r/Bittboy
Note: If this returns "Access is denied," the card’s physical controller may be permanently damaged.