That sounds like a network discovery issue, especially since Roon itself can reach Tidal but the native Tidal app cannot connect on the same setup.
This is something you’ll want to get in touch with Tidal directly for the best next troubleshooting steps. Perhaps rebooting your machine failing to connect, along with your primary router may help.
Roon works with Tidal via the Tidal API, which is a separate network pathway from their own native app.
If you’re not able to log in to Tidal via their webpage directly, we’re unfortunately limited in our ability to assist here. You’ll need to reach out to them directly.