UE4_Mannequin_Skeleton.uasset failed to save

I tried to create a death animation and when I replaced the mannequin from the animation starter pack with my mannequin, it shows up this message:

The asset
(UE4_Mannequin_Skeleton.uasset) failed
to save.

Cancel: Stop saving all assets and return to the editor.

Retry: Attempt to save the asset again.

Continue: Skip saving this asset only.

Can I somehow save the mannequin skeleton? If I don’t save it, the death animation won’t work.