Apple - How can I make my microSD card writable?

I had a PNY 32gb SD Card. Spent hours trying to find out how to make it re-writeable. Well the answer is simple. The slider on the left side of the card must be "up" (the read-writable position) BUT ALSO the tiny "notch" opposite the slider must be covered with a piece of tape. It's really the opposite of the old video tapes, which we had to break the tab if we did not want anything recorded over it. But I can guarantee you I've bought a lot of SD cards and have NEVER had a card that was write-protected out of the package that required me to do anything but raise the slider on the left side.

I've encountered the same. Ended up doing this:

1. Backup the SD Contents
2. Format the SD as FAT16 using Disk Utility and Terminal

following these steps:

1. Unmount (not eject) the SD from Disk Utility and copy the id (doing CMD+I on the SD and then selecting the Disk Identifier value (e.g. disk2s1))
2. Format to FAT16: sudo newfs_msdos -F 16 /DEV_PATH/TO_SDK so in my case: sudo newfs_msdos -F 16 /dev/disk2s1

HTH