Currently exporting a mesh from Salome to Gmsh format with meshio exports it into the gmsh binary file format version 4.0. This combination is a bit unlucky due to issues with the gmsh 4.0 format; in fact, not even gmsh can read a binary gmsh 4.0 file.
The solution would be to export to gmsh 4.1 format [binary or ascii] or to gmsh 4.0 ascii format. To export in ascii one needs to provide the --ascii flag to the meshio call.