February 2023: How To Fix Connection Problem or Invalid MMI Code On Android 2023?

How To Fix Connection Problem or Invalid MMI Code On Android: A connection problem or invalid MMI code is the number one issue that Android device users face. If you’re facing the same issue, don’t worry! This blog will help you to fix the connection problem or invalid MMI code on your Android device. We’ll overview the different possible causes of the connection problem and provide troubleshooting tips to solve it. Let us help you get back to using your Android device the way it should be used – with a stable and error-free connection!

MMI codes are not used regularly by mobile users, but when they are used their proper function is extremely important. Therefore, when an Android user sees a message saying “Connection problem or invalid MMI code” it must be high frustrate. This error stops them from making certain calls and sending some text messages until they solve this issue. Fortunately, there are multiple solutions for this problem and you can try them one by one if you are encountering this issue on your Android phone.

What are MMI Codes?

Man-Machine-Interface or MMI codes are Android phone codes that contain characters like a hashtag (#) or asterisk (*) in them. All the MMI codes have some kind of similarity, but this does not mean that they are the same. These codes fall into different categories based on the different actions they must perform.

Primarily there are four types of MMI codes:

  • SS Codes: The Supplementary Service Codes are hard codes for every mobile around the world and your network operator cannot change them. These codes are used to control features like number presentation, call forward, etc.
  • USSD Codes: The Unstructured Supplementary Service Data Codes are the codes designated by the service provider. These codes are sent to the network provider to access information like prepaid card balance, call plan details, etc.
  • Manufacturer MMI Codes: These codes are defined by the mobile manufacturer and are specific to your mobile model. These codes are used for operations like resetting the Android device, activating the service menu, etc. You do not have to press ‘send’ after entering these codes as they are executed as soon as the last character or digit has been entered.
  • SIM Control Codes: These codes are used to change the SIM details, such as its PIN code.

As you must see there are several types of MMI codes and the invalid MMI code error must be caused due to the proper function of any of these code types.

How To Fix Connection Problems or Invalid MMI Code On Android

Every now and then, you must play into the Connection Problem or Invalid MMI Code pop-up error on your Android device. This generally happens when a user is trying to send a Man-Machine-Interface code. What is an MMI code you ask? It is those funny codes you enter on your dial that include an asterisk (*) or hash (#) characters, like a call on your Verizon Wireless phone to check account balance, or sometimes it is just a prefix code you enter before a mobile number.  If the Connection Problem or Invalid MMI Code problem is driving you nuts, we got a few solutions that should solve your issue. How To Fix Connection Problem or Invalid MMI Code On Android.

Simple Reboot

Simply turn off your mobile (tap the Power button for a few seconds) and reboot again, see if that helps in fix the connection problem or invalid MMI code on your mobile. This Method 1 must sound simple, but sometimes that’s all it takes to get rid of the invalid MMI code error.

Reboot in Safe Mode

By using your mobile in safe mode, you must better troubleshoot your phone since it will play just the stock Android program. By eliminating all other apps playing in the background, you must test to see if the invalid MMI code problem persists without other apps working through app disable. Safe mode will disable pre-installed apps and services that came with the mobile.

So to solve the Connection Problem or Invalid MMI Code issue.

To reboot in safe mode or enter safe mode, follow the steps:

  1. Turn off your phone.
  2. Press and hold the power button to turn it on, and continue holding the power button until the logo display appears.
  3. Press and hold the volume down button until the reboot is finished.
  4. You should see “Safe mode” at the bottom left corner of your display.

A combination with the Home button might be needed for this process. Contact your mobile manufacturer to verify or check the manual that came with the mobile. Once in safe mode, try to enter the MMI you were using before to see if the problem persists. If you do not have an issue sending the text message at this point, then most like the culprit app that may have recently installed is causing the conflict.  You must start by uninstalling the most recent app and go from there.

Add a plus sign (+) or comma (,) to the code

Trying to add a comma at the end of your code and dial again, a USSD code for example, if you were trying to dial *1234 then try dial*1234, you must add a comma by holding the asterisk (*) button for about 3-5 second. Check if the error is gone after you add a comma at the end of the prefix.

Or try to add a plus (+) sign after the asterisk (*) sign in your code. This process forces the operation to look for the invalid MMI code error. For example, if you were dial*1234 then try dialing *+1234 you must get the plus (+) plus sign by holding zero for about 3-5 seconds. The plus sign should get rid of the error message and allow the call to go through. This process forces the operation to look for the USSD code error.

Check Network Settings

You could be getting the Connection Problem or Invalid MMI Code error because you are not get reception. Try to set your wireless provider, go to:

  1. Settings
  2. Network Connection
  3. Mobile Networks
  4. Navigate to Network Operators
  5. Search Networks and select your wireless provider

You must want to try this method 2 a few times before giving up on it. It must take a few tries before it connects to the available network. If the network operator search does not find your carrier or service provider, then you must want to check your SIM card for possible problems that must interfere with the network or SIM authentication.

Check Sim Card

If you have a dual sim phone, you have two choices here.

  1. Disable one of your SIM cards and activate only the SIM that you plan on using to send the MMI code. The mobile must not use the correct SIM card if you have both SIM cards playing together.
  2. Under your phone’s dual SIM settings, find the voice call setting by tapping on the menu. There it should give you the option to select which SIM card to use or “Always ask”, choose that “Always Ask” option. When you try to dial the MMI code, the mobile will prompt you and ask which SIM you want to use, that is why you will have the option to select the correct SIM card.

If you have a traditional single SIM phone, try something simple like pulling your SIM card and blowing on it, wiping it down a little, and plugging it back in. See if that will re-establish a connection.

Turn on SMS over IMS

This step is for the tech geek and we would not get into detail on how to do it since any wrong move using this method could destroy your mobile, or just cause more headaches to undo. It is basic and involves you using the Android secret code *#*#INFO#*#* or dial 4636 in the dial aka *#*#4636#*#* to enter the Android Test Menu or information mode, this is where professional technician goes to geeks out on your mobile information or device information. You must play a ping test and activate the radio and turn on SMS over IMS here that could solve your “Connection Problem or Invalid MMI Code” problem. If you really want to try this method, feel free to google “how to turn on SMS over IMS“.


If you are experiencing connection problems on your Android device, the first step is to troubleshoot the issue. This blog will guide you through the different steps you need to take to fix the connection problem or invalid MMI code. Make sure to keep the following tips in mind to get your device back up and running as quickly as possible. Thanks for reading.

compiled by the technical support officer and cited from Karna Taka Open State University


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