There is no evidence of a "verified" or official firmware download from a reputable brand called "MXTronics." Most cards labeled with "MXT" or similar generic identifiers are known to be counterfeit or "expanded" cards
SD cards contain an internal controller that runs specialized firmware to manage data. Unlike digital cameras or 3D printers that frequently receive user-applied firmware updates via SD card, the card's internal firmware is almost never updated by the end-user. Recommended Troubleshooting Steps
A “verified” download is useless if written incorrectly.
Repair the firmware that communicates between the flash memory chips and the host device.