If you run your own sim you need to open your OpenSim.ini file and go to this section:
;# {meshing} {} {Select mesher} {Meshmerizer ZeroMesher} Meshmerizer
;; ZeroMesher is faster but leaves the physics engine to model the mesh
;; using the basic shapes that it supports.
;; Usually this is only a box.
;; Default is Meshmerizer
meshing = Meshmerizer
; meshing = ZeroMesher
;; select ubODEMeshmerizer only with ubOde physics engine
; meshing = ubODEMeshmerizer
and make sure the
; meshing = ubODEMeshmerizer
has a semi colon in front of it and the line:
meshing = Meshmerizer
does not. Then restart the region and your houses should have doorways you can walk through.
If someone else runs your region(s) for you, you can ask them to do that for you.
like(0)