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 Causes the MMI Error to Occur?

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 different 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. Check Network Settings

The steps to access your network settings will differ, but the concept is the same. Follow along to check your network settings.

1. Go to Settings.
2. Now, select Network Connection.
3. Followed by Mobile Networks.
4. Then, Network Operators and Wireless Provider during the search.
5. You might have to connect again for another 3-4 attempts before it starts working again.

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. 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#).

5. 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.

Android MMI Code Error Resolved

In closing, there are a few methods/options you can take to remedy the MMI error on your phone, some a little more involved than the others. While most MMI errors occur on dual-SIM phones, it also appears 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.