USSD codes are a combination of numbers and two special characters * and #. When you dial them on your handset, you will get information on current balance, validity, current plans, etc from your telecom service provider. Each and every operator has defined a fixed set of codes.
Before it is sent to the operator’s server, USSD characters are converted into machine readable format by an application called MMI parser. Sometimes, the parser may fail to convert the code, and it will throw a USSD code running or Invalid MMI code error.
If you’re facing this problem on your Android OS powered HTC, Samsung Galaxy, Sony Xperia, Xiaomi, LG or any other Nokia phone then please try the below four solutions one by one.
Fixing USSD code running and Invalid Code errors:
Reboot your handset and redial: This option resets your GSM/WCDMA network connection. It will also stop or restart the application which is blocking your requests.
Check network signal strength: If signal strength at the current location is below 40% even after restarting the phone, move to some other room, place and redial the code.
Append comma or add plus sign (+) as a prefix: Suppose *367# is the USSD code that you’re trying to run. Change it to *367#, or *+367# and redial it.
Check IMEI: To know your handset’s IMEI, simply dial *#06#. If your device has 2 SIM card slots and if only 1 IMEI number is displayed, move the SIM card to the other slot, restart your phone and dial the USSD number again.
Please share the above methods with your friends if it has solved your problem.