Connecting two herelink controllers to obtain same feed from one camera

Hello, I want to connect my camera feed on two different herelink controllers. I am using hdmi 1 port on the airunit and have successfully paired both the controllers but cant seem to stream the video on the slave controller. It is showing “waiting for video”. I think both the qgc on the controllers need to be of the same version. Any solution on how I can update the ggc firware on herelink. Please suggest any other method, if possible.
Thanks in advance.