Activating SFP Port

Hi

I have the Zyxel USG Flex100W and would like to use the SFP port to link it to my Zyxel Switch. However since the recent firmware upgrade, this device is no longer able to be managed on Nebula and the WebUI does not seem to allow the addition of the SFP port to the LAN Interface/Group. Any suggestions on how to do this?