one side of the house doesn't appear

when i import house from blender in (.blend, .dae, .fbx)
there are two sides when i go right i see the side when i go left it seems to be that the roof is on the air the side doesn’t appear?

Check your normals in blender. Only one side of each triangle is allways showed while from other side triangle is transparent. If your normal is not calculated correctly, your wall would be transparent from outside. Check how to work with normals here:

Learn more about normals here or browse around a little.