the same question today 2021/3/18
Hi, I have the same problem. I can login to Tidal account but whet it comes back to roon it says “Log in” Tried to restart everything including my router …nothing helps. Problem started today 
I just cant wait for Tidal connect for windows to be released, then I will stop my Roon subscription as I use roon mainly to stream Tidal and it this case its a waste of money form me.
There is a thread in #support about this problem. Roon are aware and are working on it
Please add further posts there. Closing this thread.
I join the community of users which currently have to learn to live without Tidal via roon 
roon does not show a single Tidal album. The problem first occured this morning. I have no problem when using the Tidal app or the Tidal web player. The last days very often two messages already mentioned above were indicated: “Too many failures stopping playback” and “This track is not currently available in Tidal”. I am not sure, but may be this error message occur only when playing certain albums.