Share a model with external organisation

I have created a project in Contextshare and successfully uploaded a 3SM model which I and other internal team members can see.

I have shared the project with a couple of external organisations who have clicked on the invite link and can successfully see the 'project' but cannot see any models within it. There is no tick next to contexshare.

I have set the model to 'public'

Any idea why external organisations cannot see my model?

Thanks