I imported a mesh, but the reversed normals are not showing.
How can I make the mesh visible from both sides?
You can set backFaceCulling=false in the mesh material so that back faces are displayed. A playground can help if you can make a repro
I imported a glb file and not assign material in babylon.
You can go to the sandbox, upload your glb file and tweak the material parameters with the inspector. Once you found what works, you can access the object by name, get the material, and perform the necessary changes.
Other solution, you can import your glb in Blender, make it double sided, export back to glb 
1 Like