i’ve had this problem with a few of mine as well, what i found works for me is go into edit mode on each of your meshes(if you have multiple) hit space, type in “add uv map” then go to the tabs at the side and find recalculate, then export the mesh again and on your fbx tab at the bottom left, under geometry tab, there will be a shader option, it will say normal, change it to face or edge.
If this does not work, make sure all of your faces are not overlapping at anypoint in the mesh, it causes problems in unreal from blender.