Some Siemens' cooktops -- cooktop-only models or oven/range models with attached cooktops -- have a control panel lock that you can turn on to prevent use of the hob burners and control panel. This lock is set via the control panel and/or with the removal of a magnetic temperature dial that locks the burners if they are removed from the cooktop. Siemens designed the cooktop lock feature to prevent injury while cleaning or to children using the control panel and/or dial, if applicable, without permission.
Press your Siemens' hob control panel "Panel Lock" or "Cooking Mode" key for at least five seconds. If your cooktop doesn't have one of these keys, press the "Power" or "Power Off" key. If your cooktop has a "magTron" dial that you removed when you locked the cooktop, return the dial to its original position and then press one of the keys.
Turn on a hob burner to confirm that you've successfully unlocked the hob.
Flip the circuit breaker switch for your Siemens' cooktop, oven or range to power off the appliance completely and reboot the control panel if you still can't use the hob. Wait five minutes. Flip the switch, reset the clock and then turn on a burner.
If you can't unlock the hob, contact a Siemens' certified repair specialist for assistance, as the hob control panel has likely malfunctioned.