To use the Open Mode with the MG80 Pro off-camera the flash must be set to the 'SL' slave mode. To confirm that your MG80 Pro is set to the 'SL' mode; with the flash turned on, press and hold the power button for 3 seconds to display the mode selection screen 'On', CO', or 'SL'. Rotate the dial to 'SL' then press the center of the dial to confirm.