[Windows Central Question]

it happened after upgrading to win8.1 .please reply

[myst02]

Hi,
I would recommend backing up all data and doing a hard reset.

Here's how to do a hard reset:
1. Turn off your phone
2. Press Vol Down + Power + Camera buttons
3. An exclamation mark will appear on the screen
4. Press these buttons in the following order: Vol Up,Vol Down, Power, Vol Down

[RumoredNow]

Your SIM may have gone bad. Is there another phone you can try it in?

​Check with your carrier for a new SIM.