1) Please check that there should not be any geometry issue (like intersection , non-planar surfaces or external holes etc.).
2) Please check that , in Model browser , there should not be any room below local shades. If it appears please change its property to first to local shade & then to 'Room' , once the room is placed at its proper position in model browser , you can try for simulation.
3) If you are using any older version of IES<VE> then I would strongly recommend you to use latest IES<VE> versions.
If the problme still persists , please send us a model at support@iesve.com , so that we can have a look at it.
I hope this has been of some help.

