My Book for Mac was read/write for me during 2017 (last written to April 2017). This year, it is read only. I have changed nothing on the drive that I am aware of. I have upgraded to Sierra and then High Sierra in the interval. I cannot write to it any more. I bought the 4T drive so I could load movies and other large files. 85% of it is free space. What’s happening? I appreciate any help so I can again write to this large drive.
Hi pyonemura,
Read Only error issue would be caused due to the incompatible system file format of the drive. It is required to check the file format of My Book and change it to MacOS compatible file format. You should refer this KBA for more details:
