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Master Unlock Code Unlock Instructions
Once the unlock request is processed, you'll need to:

Make sure you have an active data connection via 3G/4G/LTE or Wi-Fi.
From the Application list, tap Device Unlock. (Note: The application may be located in the MetroPCS folder.)
Tap Continue.
Choose the Permanent Unlock type:
If successful, restart the device to apply the settings.

All you need is an Android device that supports the Mobile Device Unlock app:

HTC Desire 626s,
Kyocera Hydro ELITE (C6740),
LG Leon 4G LTE (MS345),
LG G Stylo (MS631),
Samsung Galaxy Core Prime (SM-G360T1),
ZTE Obsidian (Z820).
MetroPCS Device Unlock App Tutorial

Note: If you do not restart the device, you will have a persistent alert in the notification tray.

WARNING: It is very important to mention that the customer has to have data when attempting to perform the unlock, either 3G, 4G or wi-fi but data on the phone. If there is no data the unlock will be unsuccessful, once a device has been whitelisted we will not be responsible for unsuccessful unlocks. If customer has changed the original software or IMEI we will not be responsible for the app not to work (Do not install custom firmware like Avatar or Cyanogen before unlock your phone). If customer cannot find the app on its phone he can easily go to applications and make it visible but a Hard Reset will always bring the app back to the phone.


Phones are showing 2 different messages in the screen, let’s understand them before:

1. Server not responding. Please try again later: When this happens it means that the phone is not connecting the the Unlock server, it could be a very slow internet connection, the customer has to connect to a better internet service (preferably Wi-Fi). OR 2. Unlock Failed. This mobile device is not elegible for unlock: This means that the IMEI is not Whitelisted with the RSU server. We have to run RSU unlock. Some unlocks are taking up to 4 hours.

If any of the Leon come up with the server not responding error, then you should try all of the following since it is not an unlock problem but it is a phone software problem:

1.- Try another wi-fi with better (faster) internet service.
2.- Try updating to the latest android version.
3.- Try doing a master reset.
4.- Try flashing to the latest version of the LGMS345 version 10d.

Also this method is proven to solve the Server Error on the LG Leon.
http://androidforums.com/threads/unbrick-guide-lg-leon-lte-metropcs-lgms345-kdz-firmware.923914/