I have no idea what's wrong but depending on the day or the project the Ram Preview function is not working.
I tried restarting, I tried using the shortcut or the button on the preview tab. I even tried removing some layers to see if there was a problematic one.
The thing is ohter times it just work fine.
Does anyone have any idea?
Even though I just had regular 3D layers with no extrusion the Ram preview did not work. Switching to Ray-traced 3D seems to have solved the problem.
Moved from the Creative Cloud to the After Effects forum. Even though you seem to have a solution others may be able to contribute alternative solutions.
Your posts are devoid of any useful info like system specs, comp settings, what footage is used and so on. Nobody can even begin to guess.