Report content not visible - dataset from a different workspace

Hi again,

So our organisation is fairly new to BI Service. All employees have a Pro licence as part of their Microsoft subscription (I'm not a techie so don't know the full details).

We have set up a number of workspaces, and a number of different apps. Each workspace has a few datasets. All security for datasets and apps appear to have entire organisation as viewers/ App (Reshare) etc. I cannot see an issue there, when both datasets, workspaces and apps have the same permissions.

So "workspace 1" has reports in it using a dataset from "workspace 2" (along with reports from its own datasets) and the reports are published to dashboards, through to App 1.

"Workspace 2" has reports in it using a dataset from "workspace 1" and the reports are published to dashboards, through to App 2.

App 1 was deployed in January 2020. App 2 was deployed in March 2020.

All reports in App 2 are viewable by the entire organisation. But, our users cannot see the content of the new dashboards in App 1 that use a dataset from App 2 due to permissions:

I took a copy of the report and saved it to workspace 2 (where its dataset is), republished dashboards and apps, and everyone can see the contents in App 2.

I'm at a loss, don't know if it's "new workspace" vs "classic workspace" or maybe a tenant setting. Any ideas would be very helpful.

Thanks everyone.