Unable to download Semantic Data Model

Hi. Before checking the considerations, let's consider prerequisites. The most important one is checking with your Fabric Administrator if the settings at Tenant allow to do this. You can prevent this action for group of people:

You can also validate it publishing a simple report connected to a file very fast. If you can't download it too, then the setting must be blocking you. If you can download the sample simple report, then there is a consideration you might be breaking.

Consider that you should check the Report considerations and not the semantic model or dataset ones. You can't download a dataset of a live connected to SSAS because the power bi dataset kind of doesn't exists. The real one is hosted at SSAS and that's not a PowerBi semantic model. If you want to try downloading the report to edit the visualizations, you can if the settings are correct, but if you want to modify the data model, you should change it over SSAS.

I hope that make sense