I know there are lots of similar threads but I wasn't able to find a solution and am just that close to freaking out because I've been working on a project for several weeks that I'm supposed to deliver to a customer in a few days and suddenly multicam is not working anymore.
My sequence has 3 sources. And now, only one is displayed in the multicam monitor. What I edited already plays fine though in the preview monitor (all 3 sources show up without a problem). Is this a bug?
Try closing and relaunching your Program Monitor. When I switch from my Multicam layout to my Edit layout more often than not I only see the Multicam Preview in the Program display. Command W, Shift 6 gets it back on track.