I was having the same problem in 4.24 (And I’m guessing that you are not having problems with bone names, since it just asks for the preview mesh). This is what I did:
- Open Skeleton Asset;
- Repose Skeleton Asset;
- Click on the “Apply” button under the Mesh section of your preview scene settings (Far right of the screen);
- Save the Skeletal Asset;
- Retarget Animations.
People are not actually applying the new pose so while it “looks” like it is changed in the preview window when you save it, it actually isn’t saving that new pose for the animation instances, just the preview that you are seeing. So just make sure to click the apply button, or it will not work.
Also, if you go to retarget and you do not see the original asset mesh (nothing in the first box) then this is actually telling you the pose was not applied.