It has been over 5 months since I started this thread. I have seen others posting with the same issue, yet still no fixes for this from Plex. The “My Tidal Playlists” section loads just fine, which hints that the linking of my Tidal account with my Plex account isn’t the issue.
Moving on to the “Recommended” tab… it takes some time to load, but it does eventually load.
Finally, the “My Tidal” tab. This one still does not work. Being a programmer myself, I can’t help but think that it is not a coincidence that it takes exactly 30 seconds for the error message to return (“there was an unexpected error loading this library”). It looks like a timeout is occurring for the API call, and my guess is that a) the API call is incorrect, or b) the amount of music in our Tidal libraries is larger than what the majority of people have.
I am going to go with b), as the shouting would be much louder if the API call was incorrect: everybody would be affected.