If Tidal is working for playback but not displaying album art, you may need to clear the cache of your Tidal App.
You can do this in the settings page of your phone by navigating to the App Management section.
Here you should be able to select the Tidal app and then select the option to clear the cache.
This should resolve this issue and bring back the album art on the streamer's front panel display.
Getting to the App Management section of your phone may be different depending on your phone's make and model. Generally you want to go to SETTINGS > APPS > and you should then be able to select Tidal from the list of apps you have installed here.