Microsoft has paused the accessibility of Windows 10 preview for Lumia 520, Lumia 525 and 526. It is reported that many users have bricked their Lumia 520/525/526 while updating the Windows 10 preview build using Windows Phone Recover Tool. Some users are also reporting the same problem with their Lumia 920.
If you are also a victim of this update, you should join the discussion by following below source link to get the correct solution. Some users who has already got the solutions are providing support to resolve the problem, but we will suggest you to wait for the official team to speak on the subject.
Thanks for the tip Sumit.