If your client is logging in and can't see anything in their project, it could be caused by the following reasons:
1.) Your client is accessing the site on a phone or tablet. The features on mobile devices are currently limited. For the full-featured experience, please encourage your clients to access their projects on a computer.
2.) The statuses of the items are set as "Unspecified".
In this video, I'll quickly walk you through what this means and how to solve it.