This is usually caused by the SD card’s physical write-protect tab or the computer’s card reader, not the camera.

On SD cards, the lock slider is only a mechanical flag: the card reader checks its position and decides whether to allow writing. If the slider is loose, slightly mispositioned, mislabeled, or gets nudged while inserting the card, the Mac’s reader may see it as locked even though the camera still works normally.

Try these steps:

• Flip the card’s lock switch fully the other way, then back again, and test both positions.
• Check whether the slider feels loose or damaged.
• Try a different SD card in the same Mac reader.
• Try the same card in a different card reader or computer.

If other cards also become read-only in that Mac, the reader is likely the problem. If this card is read-only in multiple readers, the card’s lock tab is likely the issue. In some cases, if the tab is broken or missing, carefully placing tape over the tab area can let a reader detect it as writable.