How come Lumia Black update won’t fit on my Lumia 925 even when I have plenty of free space?

If you have the Wi-Fi calling (TMO) feature in use in your phone, please clear the temporary files with the Storage Check app when the Wi-Fi is turned off. This will vacate more space.

  • Update the Storage Check app (to version or higher, when available).
  • Set Wi-Fi off (Settings > WLAN > Toggle off).
  • Launch Storage Check.
  • Press the Clear button to delete the files.
  • Update your Lumia to Black.

Note: You may also have too little space on the user disk. Please move some content to the cloud or other storage to vacate more space.