I have a shared data source in SSRS (SQL 2016) that has Windows credentials saved. I can click on that data source, test connection, and it works fine. However, when I attempt to use that data source in a new report it prompts me for credentials anyway.
If you look at the image below, you'll see the prompt window I'm referring to. If I click Test Connection on that screen it works too so I don't understand the issue!