@Judyfax,
Please help us understand your setup and intended use:
1.) Do you have the H920, or is it an H920+ ?
2.) Is the main controller an ST24, or is it an ST16?
3.) Does the CG04 show up on the camera select list of your main controller?
4.) What firmware is currently loaded on the ST12?
5.) Does the ST12 show the V18 camera on the camera select list?
6.) Are you trying to fly the H920 using the ST12 only, controlling both drone and camera?
7.) Are you trying to fly in team mode with ST12 controlling the drone, main controller controlling camera?
8.) Are you trying to fly in team mode with ST12 controlling camera, main controller controlling drone?
I am not at all sure you can do the things you want to do. The only information I have are the owners manuals for the H920 and for the H920+. I doubt I fully understand how the systems were intended to be operated, but it does not appear the ST12 was intended to control the CG04 camera.
Once the system and intended use is defined, perhaps someone more familiar with the H920 series can provide more accurate information.
A question for those familiar with flying in team mode:
Is it a good idea for the drone pilot to have a camera view on the pilot's controller screen?
(It just seems like a bad idea. Since someone else is controlling camera angle, it seems like having an on-screen view would be confusing to the pilot, possibly resulting in bad control decisions.)