How to Fix Connection Problem or Invalid MMI Code on Android Device

Sometimes, a message saying “Connection problem or invalid MMI code” shows up and can be frustrating for Android users. When the invalid MMI code message appears, it generally means that you can’t make calls or text messages until the issue gets resolved. This can occur for many reasons.

Fortunately, there are several ways to potentially fix the Android “Connection problem or invalid MMI code” error. Try the following options below. If one process fails to resolve the problem, move on to the next one.

What is an MMI Code?

Any SIM-compatible device has a plethora of codes and numbers it can be difficult to identify the purpose of each one. An MMI code (Man-Machine interface code) begins with an asterisk (*) or pound (#) sign that lets users enable or disable various star code functions (*#06# to reveal IMEI, for example).

There are several reasons why the “Connection problem or invalid MMI code” error message appears on your phone. The main reason is an issue with the carrier provider or problems with the SIM authentication on the smartphone. The error is quite common for phones with dual-SIM capabilities, but it does occur on others too.

Ways to Fix the MMI Code Error

Several methods exist to fix the “Connection problem or invalid MMI code” on an Android device. We’ll cover them from the simplest method up to the more complicated ones.

1. Restart the Android Device

The first way to try to fix an invalid MMI code would be to restart the smartphone.

1. Hold the Power button and the Home button at the same time until the phone turns off and starts vibrating; wait for it to restart. 
2. Alternatively, press and hold the Power Button until the Shutdown options menu appears, and then select Restart.

2. Run Your Device in Safe Mode

It’s possible that third-party software is interfering with your connection and causing an MMI error. Fortunately, it’s easy to rule this out. Here’s what to do:

1. Restart your phone in Safe Mode. You can do this by holding the power button (button combination) on your Android device. Then, long-press the Power icon.
   
2. Tap Safe Mode from the menu that appears.
   
3. Now, use your phone in Safe Mode for a bit to see if the MMI error appears.

If your phone doesn’t throw any error codes, third-party software is interfering with your network. You’ll need to start removing third-party apps. Start with the applications you installed around the time you started seeing the error.

When you follow the Settings>Apps path scroll down and uninstall any apps you believe may be the culprit. Then, power your phone out of Safe Mode and see if the error appears. Keep doing this until the MMI code ceases.

3. Use Airplane Mode

Some users have had success using Airplane Mode to resolve their MMI code error issues.

1. Go to Settings and turn Airplane Mode to On.
   
2. Wait about 10-30 seconds, and then turn Airplane Mode to Off.

Given that an MMI Code error can occur due to weak signal strength performing this can reset your connection and correct the error.

4. Reset Your Network Settings

Because we know that the MMI error indicates an issue with your device’s cellular connection, the next logical step is to reset your Network Settings. Perhaps your network settings haven’t updated properly or there’s a glitch in the system. Performing a network reset will clear any problem codes and help you start fresh. Here’s what to do:

1. Open the Settings on your Android device. Then, tap on General Management.
   You can also use the search icon and type Reset to skip step 2.
   
2. Scroll down and tap on Reset.
   
3. Tap Reset Network Settings.
   
4. Tap Reset settings to confirm. Your phone will restart.

When your phone powers back up, the error should disappear.

5. Modify the Prefix Code

Another way to fix the Connection Problem or Invalid MMI Code on an Android smartphone would be to add a comma at the end of the Prefix code. When a comma gets added, it forces the operation to execute and overlook any error.

Below are two different ways to modify the prefix code.

1. If the Prefix code is (*2904*7#), then add a comma at the end, similar to this (*2904*7#,).
   
2. You can use the + symbol after * similar to this  (*+2904*7#).

6. Activating Radio and Turning on IMS over SMS

1. Go to the Dial pad.
2. Type in (*#*#4636#*#*) NOTE: No need to press the send button, it will automatically appear in the Service mode.
3. Enter Service mode.
4. Select Device information or Phone information.
5. Select Run Ping test.
6. Click on the Turn Radio Off button, and then the Galaxy will restart.
7. Select reboot.

Frequently Asked Questions

Hopefully, your MMI error is gone by this point. But, if you still have questions, keep reading.

Do I need to get a new SIM?

If you’ve tried all of the fixes above and the error continues, you may need to contact your cell phone carrier for more information. They may recommend a new SIM or they can resend OTA (over-the-air activation).

Android MMI Code Error Resolved

In closing, there are a few methods/options you can use to remedy the MMI error on your phone, some a little more involved than others. While most MMI errors occur on dual-SIM phones, they also appear on phones with one SIM due to weak signals or tower network issues. If the above solutions don’t work for you, contact your service provider for assistance.