Sounds like you're experiencing the same issue described here - specific to the recent versions of the Spotify Android app:
Hello...
I Have wiim amp ultra on guest room, and wiim ultra at my bedroom... both device also standby with power ac plugin...
first problem i have is, when i want to stream spotify using samsung galaxy S23 (android 16) to one of them, No spotify connect is show up, only google cast is show up on both ultra... BUT this not happen when i use my iphone XS MAX, or PC...
second problem is, my SONY TV KD65X80K when i plug hdmi4 to PC or SAT DECODER,
HDMI ARC (hdmi 3 on tv) make communication failure between TV and Wiim Amp Ultra.
but when i unplug hdmi 4 and do restart on TV and Wiim amp...
IN SHORT: on Android currently, the only way to connect to the WiiM devices is through Google Chromecast, which doesn't support Losless quality. Before there was the option to choose between Chromecast or Spotify Connect (lossless supported)