Simple Reboot Simply turn off your phone (press the Power button for a few seconds) and reboot again, see if that helps in fixing the connection problem or invalid MMI code on your phone.

A different Android vulnerability discovered in 2012 allowed the execution of USSD and MMI codes by visiting a malicious page.

Unlocking hidden Android capabilities with secret dialer codes Android's secret codes operate through what's technically called Man Machine Interface (MMI) codes.