what is mmi code

An MMI code, which stands for Man-Machine Interface code, is a string of numbers or letters that instructs your device to carry out certain tasks. These codes are usually defined by the phone manufacturer for resetting your mobile device, activating service menus, changing SIM card-related details, and more. MMI codes are entered like telephone numbers and begin with a star (*) or hash (#) sign. For example, entering *#06# on a GSM phone displays the model and serial number of the phone. When the invalid MMI code message appears, it generally means that you cant make calls or text messages until the issue gets resolved. The error message can appear due to a multitude of issues, such as problems with the SIM card, carrier provider, or SIM authentication on the smartphone. There are several methods to fix the "Connection problem or invalid MMI code" error on an Android device, including restarting the device, checking the SIM card, and resetting the network settings.