I just had the same issue, previously logging in again to Tidal fixed that, this time it didn’t. So I tried to log out and back in to Roon as well, as I saw authorization errors in the logs. However, I couldn’t log back in to Roon at all. There seems to be some problems as also reported here: Can't login - roon think's i'm offline
I think they’ll fix it soon, just hang in a bit.
Edit: by now I can log in again, but my Tidal connection is still broken. I have logged in again to Tidal, confirmed the login on Tidal’s page, but I keep receiving errors in Roon along with a lot of 403 errors in the logs:
02/07 12:16:02 Debug: [easyhttp] [142] GET to https://tidal.roonlabs.net/1/featured/top/albums?offset=0&count=30&c=tidal-de returned after 498 ms, status code: 403
02/07 12:16:02 Debug: [easyhttp] [141] GET to https://tidal.roonlabs.net/1/featured/recommended/tracks?offset=0&count=30&c=tidal-de returned after 502 ms, status code: 403
02/07 12:16:02 Debug: [easyhttp] [143] GET to https://tidal.roonlabs.net/1/featured/top/tracks?offset=0&count=30&c=tidal-de returned after 501 ms, status code: 403
02/07 12:16:02 Debug: [easyhttp] [145] GET to https://tidal.roonlabs.net/1/rising/new/albums?offset=0&count=30&c=tidal-de returned after 499 ms, status code: 403
Tidal itself works just fine for me. But not its Roon integration.