The error differs slightly, which helps to find the exact object Python cannot find.
AttributeError: 'module' object has no attribute 'Model' This indicates that the model does not exist, the model name is spelled incorrectly, or there may be spaces or underscores.
AttributeError: 'module' object has no attribute 'ToolboxAlias' This indicates that the toolbox alias was spelled incorrectly, or there may be spaces or underscores.
Models that are newly created, as well as any models that have been edited and saved in ModelBuilder in ArcGIS Pro, cannot be used in other ArcGIS for Desktop applications.Therefore, attempts to call a model created in ArcGIS Pro with the ArcPy in Python 2.7, will raise an AttributeError. See: ModelBuilder: Migration to ArcGIS Pro
Solution or Workaround
The solutions are to:
ensure the model exists
ensure that the toolbox alias and model name are spelled correctly
remove spaces or underscores in the names and aliases
use the Python installed in ArcGIS Pro to call models created in ArcGIS Pro
For example, in the Toolbox Properties dialog, under Alias, remove the underscore ( _ )
The underscore ( _ ) can also be removed from the model or script tool Properties dialog, if necessary:
Once the underscores ( _ ) are removed from the toolbox alias and/or the tool name, the tool can be used in the Python window.