SD cards have mechanical locks on them that allow to your prevent them
from being written to. While this can be good for security, most of the time they just end up getting broken. Luckily, fixing the SD card will only cost you a couple cents and a minute of your time. See Step 1 below to learn how.

Step 1:

Find the lock groove.
Look for the spot where the lock switch used to be. The groove is typically located on the left edge of the SD card when you are looking at it from the front.

Step 2:

Remove any remaining lock material. If there is any
plastic piece of the old lock switch still attached or dangling, use nail scissors to gently snip out the remaining piece.

Step 3:

Get some cellophane tape.
You will need a thin, clear cellophane tape with a strong adhesive grip. Scotch brand is the most common, but any brand will work as long as it is very adhesive. Make sure that roll is not very wide. 1/2" is the standard.

Step 4:

Remove a piece of tape. Remove a small piece of tape from your roll. Remove a 1/2" piece of tape from the roll, creating a 1/2" x 1/2" square of tape.

Step 5:

Affix the tape to the lock groove. The tape should be
wrapped around both the front and the back of the SD card, creating a level surface along the edge with the lock groove. Make sure to firmly press the tape down so that there are no wrinkles or bubbles.

Ensure that none of the contacts on the back of the SD card are covered by the tape, or the card will not read.
Bumps in the tape or raised edges could cause the SD card to get stuck in the slot.

Step 6:

Insert the card into your device or reader. The should now be fully unlocked. If it is still locked, make sure that the tape has created a level surface on the lock edge.[1]