How to export multiple Mesh file (.UNV) at once

I am beginner to this platform. Now I am trying to learn using this platform with elmer.
So Elmer as in “GetStartedElmer” requests UNV file for Meshing data. I created three model and create Mesh for them.
But when I selected all Meshes and hit export-> UNV nothing happens, no pop-up window, and after several times hitting that some errors appeared


Does anyone know about this issue? And how can I export multiple Mesh at once?