OK, now I know I've gone round the bend. I'm working along, and in the time line, I collapse all the layers. Then I must have clicked something and didn't realize it, because now, all the layers are hidden! No channels are in solo, and the "shy" button is off. All my other comps are normal, so whatever I did only affected this one.
One clue: the "eye" icon to hide or show layers? It is ON, but it has no pupil, like it does on the icon bar and in all the other compositions.
Anybody have an idea what I did? I'm bamboozled!
Any chance you've entered into a layer view instead of the comp view?
Also, when you're asking for help, including things like what version of AE, what OS, etc. Could prove useful.
Collapsed transformations? Layer styles? Some adjustment layer? A matte/ alpha stencil layer mode? Could be one of those.... I suggest you provide a screenshot of the timeline and comp viewer. I'm sure it's just some simple switch you have overlooked....