Hi Dasappan,
The warning message around MB 5.5. axis orientation normally indicates that the file was saved in older version of the software which used different setup for IK/Skeleton. Typically the file should load without issue – the problem with the mesh not displaying shouldn’t be related to this. Note: for really old files, some will need to be opened in MotionBuilder 7 or 7.5 for them to open correctly in MotionBuilder 2009 or newer.
If you have Gold subscription support setup, you should contact the Autodesk Support team so they can look into the issue further.
Best Regards,
Lee