There might be any problem in the mobile itself, as because when i downloaded the same, i didn't faced any problem. Also now you can try 5.1 in some days. here are features of same:
The first feature change is quick settings tweaks. The quick settings panel has been polished up a bit in Android 5.1. Each of the icons (including the Auto-rotate option, shown over on the right) now comes to life with a new animation when you tap it.
What's more, it's now easier to hop between Wifi access points and Bluetooth devices with the new dropdown arrows next to these settings.
With Device Protection, your lost or stolen gadget will stay secured until you sign with your Google account - regardless of the fact that somebody resets your gadget to processing plant settings. This feature will be accessible on most Android mobile phones and tablets dispatched with Android 5.1 along with Nexus 6 and Nexus 9.
Superior quality (HD) voice calling is presently on your cell phones. Get crystal clear calling with HD Voice between compatible Android 5.1 devices like the Nexus 6 on T-Mobile or Verizon.
Sony has included high definition voice in past updates, giving users HD voice calling quality between compatible handsets. Obviously it will be a while, before we see this update on Sony Xperia devices – first things first, let’s get Android 5.0 rolling.
Google did not detail just what performance tweaks and bug fixes Android 5.1 brings to the table, but the latest update is expected to make everything run smoother. Nexus devices will be the first in line to get the new update, while other devices will get it sometime later.
Android 5.1 Lollipop also provides up gradation, such as the ability to join Wi-Fi networks and control of your paired Bluetooth devices directly from Quick Settings.
We hope you enjoy these tasty additions to Android Lollipop as you get more out of your Android phone and tablet.
— modified on Mar 11, 2015, 5:44:28 PM