8 Methods to Fix Connection Problem or Invalid MMI Code

There are times when you would dial USSD code on your Android phone, you would get an error message stating, Connection problem or invalid MMI code. If you get this message and do not know what to do, you came to the right place as through this article, you will learn how to fix this issue, connection problem or invalid MMI code. 

What is USSD and MMI Code?

USSD means Unstructured Supplementary Service Data. It is a protocol which is used by mobile network operator to communicate with smartphones. Example, if you wish to check your balance you would dial USSSD code such as *123#. 

MMI code on the other means Man-Machine Interface code. It is used to get information about your phone. Example, if you will dial *#06# on your phone, then it will show you your IMEI number. 

There are several reasons as to why you would experience invalid MMI code error but do not worry as this error could be solved. 

How to Fix Connection Problem or Invalid MMI Code?

Method 1 – Restart your Phone

This method is the most common method to solve different issues not only issues on phones but also with other technological devices. Hence, this method is highly recommended. 

• Press and hold power button on your Android phone. 
• Select switch off your phone
• Once your phone is switched off, press the power button again 
• Restart your phone
• Dial USSD code again 

Method 2 – Check if USSD Code is correct

There is a possibility that the USSD code you have entered is not correct. You could check it by checking or searching on Google or if you could contact your mobile operator. 

Method 3 – Launch your phone in Safe Mode

• Press the power off button
• Tap and hold the power off button on the screen
• You will be asked to activate the safe mode
• Click on it 
• Wait for your phone to restart

Method 4 – Check network connection

Another reason as to why you could encounter this issue is due to network problems. You could connect to your network manually. 

• Go to the settings of your phone
• Select connections
• Select Mobile Networks
• Select Network Operators
• Select your SIM
• Select the Manual option
• Select your SIM network operator name
• Dial USSD code

Method 5 – Change LTE to 3G/2G network mode

• Ve a los ajustes de tu teléfono
• Click connections
• Go to mobile networks
• Click Network mode
• Select 3G/2G (auto connect)

Method 6 – Activate SMS over IMS

• Dial *#*#4636#*#* on your dial pad of your phone. 
• Go to Phone information
• Select Run Ping Test
• Once ping test is done, select turn on radio
• Click Turn on SMS over IMS
• Reboot your phone

Method 7 – Add comma after USSD code

• Add a comma at the end of your USSD code example *123#, 
• To be able to add a comma, you will need to hold the star button or you could use plus symbol. 

Method 8 – Remove any recently installed app

• If you have just recently installed an app, this could be a possible cause. 
• Uninstall the app and check if the error is gone and if you do no longer experience this error, then, it could be that the newly installed app is the cause.