The two products are different. AutoCAD LT is typically used for drafting and documentation. Autodesk Fusion, on the other hand, is a 3D product design tool for parts modelling that enables integration with CAD/CAM. Although AutoCAD LT 2D drawings may be imported to Autodesk Fusion, Autodesk Fusion does not automatically transform the 2D drawing into 3D geometry.
Once a design has been uploaded to the Autodesk Fusion Data Panel, a cloud translation mechanism is used to quickly transform designs that are not native Autodesk Fusion files (such as.ipt) into the Autodesk Fusion format (.f3d).DWG files from AutoCAD and other applications can contain data that Autodesk Fusion cannot read. Autodesk Fusion can only import DWG files containing 2D sketch geometry or 3D solid bodies. For AutoCAD drawings – open the file in AutoCAD and purge the file, making sure to remove XREFs and images.