the bevelling is stopping at the point where the normals of the polys change from inward to outward – the normals should all be facing the same way (outwards is probably best – they should all be orange when selected)

the vertex selected here is really two if you zoom up close, those should be welded together.

the wall of polys visible through the hole isn’t attached to the walls, only the floor and ceiling (I moved it in the picture attached to see what it was attached to). That would stop normal bevelling at that point – it should be removed if you don’t need it or cut and attached if you do need it.
