Copying/pasting keyframes to another layer?

I used this tutorial ( https://youtu.be/aHCa0P40h6g ) to add shading to my animation using the Tone node and a duplicate layer, as described within the tutorial. The original drawings are on a layer called face, and the Tone overlay is on a duplicate layer called face_1.

I added motion keyframes to the original drawings on the face layer, and wanted to copy and paste these keyframes to the face_1 layer so that the shadows on the character would follow the motion keyframes and also so I wouldn’t have to tween both layers by hand as exactly as possible. I have my paste mode set to Keyframes Only, but when I go to paste the keyframes into the face_1 layer, nothing happens. Is there a way to fix this?

Thanks in advance!