I've been able to connect to my chromecast devices through spotify connect in the past, but as of yesterday, I haven't been able to connect to any chromecast device. I've rebooted everything and tested other apps with the chromecasts, and they seemed to work fine. I tried connecting to chromecast through the chrome browser and the spotify web player, and it connects and then immediately drops the connection. The same thing happens with the spotify app on android (running on a Pixel 2). Chrome can stream other audio content fine, it only runs into this connect/disconnect issue with the spotify web player.