Edit Linked Mesh

I have a linked character that I need to edit. Unfortunately I’m not able to keyframe its mesh unless i edit the original file, but even then the keyframes don’t update in my linked file.

I know it’s possible because I’ve done it before.

For context, I’m copying keyframes from an .fbx file and pasting them onto the mesh shapekeys. Because I can’t edit the shapekeys (because the file is linked), I have to go back to the original character file. But even when I paste the keyframes here, make sure the keyframes are working, and save the file, the character doesn’t update in the linked file.

Any help would be appreciated!