Onion Skin Tool stopped working

When I go to use the Onion Skin Tool, it doesn’t work. I turn it on, select the amount of frames I would like to show, and yet it still doesn’t appear anywhere. I’ll go to do a lip sync on a character and what happens is i’ll do the mouth, copy the frame and paste, do the traditional Alt Shift D, and for some reason even after I change something in the frame with onion skin on, nothing shows up like a red or green line that represents the previous or next frame. Any help would be greatly appreciated.

Are you expecting onion skinning in the lip sync?

Have you hand drawn the mouth shapes frame by frame or are you doing the automated lip sync process?

The automated lip sync process involves drawing substitutions. Drawing substitutions are instantaneous. As far as I know if you are just doing a series of drawing substitutions there is not going to be any tweening so there won’t be anything onion skinned.

If you were doing the lip sync by manually drawing everything frame by frame you would see onion skinning, provided you made all of the appropriate preparations (i.e. activating the feature, designating what is to be onion skinned, how many frames, etc)…