Well, please check your if your device is really connected and playing Tidal over Ethernet, you may dubble check this by switching your wifi signal completely off. Your app will not function at that time, but you are able to determine your connection to your Wiim devices will be Ethernet only.
I understand how frustrating these issues are, but i dont thinks its a typical Tidal issue.
You may try some other services that play HQ audio, ie 'Radio Paradise' source in the Wiim. Recently added by the Wiim team

( Thanks Wiim team! ) these stations have HQ sound and really pleasant to enjoy!!
Take a listen if your problem persistent " at some any or all other sources".
For me, i never had any issue with Tidal on my Ultra. Works works flawlessly, even all High rez 192/24 tracks.
However, the original Tidal app ( download at the play or app store ) may be preferred above the build-in Tidal source at the native Wiim app.
Hope your issue will be fixed very soon!
I suppose nor Tidal or Wiim can be blamed solely here. Good luck!