We have identified the issue with regard to some section properties not being recognised by STAAD.Offshore. These are sections that are classified as HSS, hollow structural sections, rather than PIPE. We should be addressing that early in the new year. In the meantime, I would recommend using defined pipe sections with the required external and internal diameters.
The transport loading module was not designed to use any loading from STAAD.Pro as additional masses, but we added the functionality to allow nodal loads and UDLs to be imported as masses from a given load case. Many of the other forms of loading are complex and requires a STAAD analysis to resolve into equivalent menber/node loading. You may find that you can define you loading in STAAD, run the analysis with the command PERFORM ANLYSIS PRINT LOADING and create a new load case with these loads which you can import in the STAAD.Offshore file.