What Roon Remote device are you using to attempt the logon through Roon?
I had an issue with the login to Tidal through Roon from my Ipad Pro and from my PC using IE as the default browser. I could login to Tidal directly with IE but not through Roon with IE.
Support asked me to try with Chrome as the browser. Didn’t have Chrome on my PC but I switched to Firefox as the default browser and the login completed successfully.
Your issue my be different from mine but if your browser is IE try Chrome or Firefox.
Update: Sorry I see you have Mac Mini i7 listed now. Missed that.