Is that warning in Blender or Unreal? I was looking at the exporter settings in Blender, and the importer settings in Unreal. In Unreal, the Import Options has an option to either “Import Normals Only”, “Import Normals and Tangents”, or “Compute Normals”. What did you choose for that? Import Normals Only and Import Normals and Tangents is for keeping what was done in Blender. Calculate Normals re-computes the normals and tangents within Unreal.