I think we'll all be guessing unless you give us at least a screen shot, and note where it isn't meshing.
i am not allowed for this project to post screenshots, but i can tell you that it is a single part. only one body present. unfortunately, the software cannot give any clues as to which part isn't meshing correctly this way.
it resulted from a procedure i have followed a couple of times now without problems. i do this because the designs are made in such a way that they are unsuitable for FEA: all plates are designed edge-to-edge (for welding) so no actual connection is recognized. i transform these assemblies to multibody parts and use lofts to fill up the gaps.
as mentioned before: one quarter of the structure meshed just fine, but mirrored twice it keeps failing. I placed it in an assembly to check for interference, but none present.
I hope you can point me in the right direction...
you have a part in an asy or a body in a part?
either way if one part meshes and the rest don't and they are coincident (not overlapping) the mesher can't mesh the interface between them
try incompatible mesh
or mirror and then merge them together
i'm also assuming this is a solid part, meaning no problems with CTRLQ with VOR and also no imported errors with no features in the part...etc