Forum Post: Cannot create Xnet,In the model assignment dialog the Auto setup button is disappeared .

When I wanted to create XNET, I found that the auto setup button of the model assignment dialog disappeared. Even if you manually assign a model, you can't create XNET in the constraint manager. I use database check and update DRC is also useless.In other file ,then button appeared and enable to creat XNET . Is there a switch to start XNET? Why is autosetup gone? What should I do? Thank you