It is a requirement for any kettle that bears the Underwriters Laboratories (UL) seal (as all Brewista kettles do) to automatically shut off the keep warm feature when the kettle is removed from the base. This is a required safety measure to prevent users from heating an empty kettle. It is not possible to disable this safety function.
To restart the keep warm function, simply press the Keep Warm button once the kettle has been returned to the base.