When I double klick on the Model in Navigation part I see in content part this unable to render... msg.
Release : 21.2
Component : Spectrum OneClick
The customer customized the model to make it a stack model.
The " Unable to render topology" error come from how they modelled the device or customized it afterwards. If they model by ip, the problem does not exist but whatever steps they took to change the model class has caused this problem.