An unmountable SD card can occur due to issues like file system corruption, improper ejection, physical damage, or malware attacks, making the stored data inaccessible. However, data recovery is still possible with the right guide. Start by checking the SD card on different devices to rule out compatibility issues. If it remains unmountable, avoid formatting or further writing to the card, as it can overwrite recoverable data. Use a reliable data recovery tool designed for SD cards to scan for lost files. These data recovery software can retrieve photos, videos, and other documents by accessing the card's raw data.