Had to restart my client as well. Just a re-login didn’t do the trick.
1: Check to make sure Tidal is still linked in Plex account settings https://plex.tv/users/other-services (mine was not)
2. Remove the client from “Authorized Devices” in Plex server settings https://app.plex.tv/desktop#!/settings/devices/all
3. Close that client
4. Restart client + sign-in
