Looks like Part 1 is the problem part. The error message reports that Part 1 is not a solid object.
There could be two issues:
A) You are trying to Solid mesh a Surface part. the fix for this is straight forward. Change the Mesh setting for part 1 to "Part settings" and change the mesh type to surface
B) Part 1 (even though it was modeled as a solid object) was imported to Autodesk Simulation Mechanical as a surface object. if this is the problem, try to import the geometry to simulation mechanical using a different format such as STEP or SAT, or try to fix the original CAD model using Inventor Fusion
If you are still having issues please send your Autodesk Simulation Mechanical Archive file and the CAD files to our tech support department.
Sualp Ozel, PE