I am a little confused here. Did you restart the application and tried to import the model? This should have worked as you were able to see the model before. Kindly let us know which AEDT version you are using.
Please go through the following recommendations -
- Did you observe any errors in the messages windows after the fresh import?
- Are the objects of the model are imported as 3D models or as 2D surfaces? Please share the screen shot of the model along with the model history tree window with details of all the objects as far as possible.