4 Fixes for Connection Problem or Invalid MMI Code

While the location of settings and options are different, the issues and fixes below are the most common causes of the error.

What is an MMI Code?

An MMI code is the special characters such as Star (*) or Pound (#), which are used for commands on a cell phone network.

MMI is short for Man-Machine-Interface and are available for a variety of functions and options.

What is a Connection Problem or Invalid MMI Code?

An invalid MMI code is a mobile network error that has a range of problems, from connection issues to authorization issues.

It mainly is a problem with a SIM Card and is an error that happens commonly with Dual Sim Card smartphones.

There are several fixes that can solve the issue from manually switching the network such as 4G LTE or 5G, to clearing out old data.

The most common problem with a MMI Code Error is the smartphone SIM Card having a problem with authorization on the mobile network.

The error is the same with both physical SIM cards and the new eSIM types.

While eSIM is very convenient, it is still an authorization code that a physical SIM card will also have.

4 Fixes for Connection Problem or Invalid MMI Code?

1. Restart the Smartphone

If you haven’t already, restarting the smartphone can often get it working again.

The phone may have an error which a restart will often clear when reset.

2. Clear Mobile Data and Cache


The next option is to clear the mobile data and the cache. This data may have bad information that is causing an error.

Go to Settings–> Applications–> Contacts–> Mobile Data.

Choose the options to Clear Data and Clear Cache.

After clearing the data check to see if the phone works, if not try the next method.
 

3. Turn Off One SIM Card


If you have a Dual SIM card smartphone turning off the unused SIM Card can often solve the problem.

If available, look inside Sim Card Manager for the options.


Turn off the unused SIM Card and test to see if the error clears.

If you are unsure which SIM Card is unused simply test each one, on and off, to see if it works.
 

4. Change the Mobile Network Band

Changing the mobile network to another band is a common fix.

Which mobile network will work, depends on the location and will vary.

For example, 5G will work in one location while the older 4G will work in another.

Below are the methods to change the mobile network on Samsung devices and Huawei smartphones.

The location to change the network can vary from phone to phone.

How To Change the Mobile Network Band Samsung Smartphone

• Go to Settings
• Click Connections
• Click Mobile Networks
• Change the Mobile Network to another Band. (Often each band is tested to see if the phone works.)



How To Change the Mobile Network Band Huawei Smartphone

1. Go To Settings



2. Select Wireless & Networks



3. Select Mobile network



4. Select Preferred Network Type



5. Chane the Network to GSM/WCDMA Auto

Summary
If you get the error “Connection Problem or Invalid MMI Code” on your smartphone it can no doubt be very annoying.

The first step is to restart the smartphone to see if the error clears.

Next, try to clear out old mobile data and the cache which sometimes fixes the problem.

If you are using a dual SIM card smartphone disabling the one not currently being used can also get the phone working properly again in some cases.

And lastly, changing the phone’s network band can also be a solution.