With the official release of iOS 9.3 to
public last week, Apple had re-released the update software version of iOS 9.3 13E237 to
fix some activation lock bugs on older devices which doesn’t allow those
devices to install the newest version on older iOS devices. 
Apple had re-released the update software version of iOS 9.3 13E237 to fix some activation lock bugs on older devices
The software is
still version iOS 9.3, only the software build number has been updated to 13E237
which fixes the activation lock issue.
The update is available through
over-the-air (OTA) release, or via iTunes.
Those who are stuck on the activation lock
screen, enter your iPhone or other iOS devices into DFU mode and connect to iTunes
 and install the new software version of
iOS 9.3.

You can download the new build version of iOS
9.3 from our download page.