# Prev working MyBook is suddenly "read only" **URL:** \ **Category:** External SSD for macOS\ **Created:** [March 10, 2016, 4:14am UTC](https://forums.sandisk.com/t/prev-working-mybook-is-suddenly-read-only/396326 "2016-03-10T04:14:02Z")\ **Posts on this page:** 3\ **Page:** 1
**Author:** ![Jaymie\_Pennington](https://avatars.discourse-cdn.com/v4/letter/j/47e85d/32.png) [@Jaymie\_Pennington](https://forums.sandisk.com/u/Jaymie_Pennington)\ **Post date:** [March 10, 2016, 4:14am UTC](https://forums.sandisk.com/t/prev-working-mybook-is-suddenly-read-only/396326/1 "2016-03-10T04:14:02Z")
I am using El Capitan 10.11.3 Previously the MyBook 2TB was working fine but now will not back up in TimeMachine and is read only. I have gone to Get Info and tried to change the permissions but despite unlocking it, I cannot change to read and write. What can be done without having to reformat the external drive. It was working and then suddenly it wasn’t. ---
**Author:** ![lluna](https://sea2.discourse-cdn.com/sandisk/user_avatar/forums.sandisk.com/lluna/32/29733_2.png) [@lluna](https://forums.sandisk.com/u/lluna)\ **Post date:** [March 10, 2016, 6:12pm UTC](https://forums.sandisk.com/t/prev-working-mybook-is-suddenly-read-only/396326/2 "2016-03-10T18:12:47Z")
Hello, you can go into disk management and run a first aid and make sure that the “Fix Permission” toggle is on. ---
**Author:** ![JimLewis](https://sea2.discourse-cdn.com/sandisk/user_avatar/forums.sandisk.com/jimlewis/32/49292_2.png) [@JimLewis](https://forums.sandisk.com/u/JimLewis)\ **Post date:** [March 10, 2016, 9:24pm UTC](https://forums.sandisk.com/t/prev-working-mybook-is-suddenly-read-only/396326/3 "2016-03-10T21:24:47Z")
You cannot do that if the IMac does not recognize the drive. Since installation of ElCapitan, the IMac does not recognize that the MyBook drive is attached via USB.