How to connect my report to my Dashboard?

I've got a workspace with a number of sheets and reports, from a template set.

I've created a new report which I can see in the workspace (I cloned it from one of the templates provided). I have confirmed that I am the owner of the new report.

I'm trying to add a widget to my dashboard, from the new report that I've made. However when I click the "+" sign to add my data source, the report does not show up in my workspace. When I cancel out, I can still see my new report in the actual workspace.

What do I need to do to add the data source to my dashboard?