External Hard Drive became Read Only
After updating to macOS Sierra on Macbook Pro (Retina 13", Early 2015), my Toshiba External Hard Drive became Read Only.
Had to update NTFS from here: https://www.tuxera.com/ntfs-drives-and-macos-sierra/ and Restart. Working fine now.
MacBook Pro with Retina display, macOS Sierra (10.12)