I’ve had the same issue with Spotify disappearing from my Home Screen, however the fix of updating or restarting is not working. I’ve checked for updates, I’ve restarted and it’s still not there. In Streaming Channels it says the channel is still installed and I can access the app but I can’t get past the account select screen (which is new).
As of 9/17 I noticed the issue as well. I was able to re-add the channel after a system restart but I could not login. I tried the system update, but I must have already received the update on 9/16. When starting the Channel the login screen came up but when clicking on my username which was already linked to the Roku, it would not login, just sat there.
I had to take the additional step of removing my account, then logging in. I went the route of opening the app on my phone and playing on the device. My credentials were then associated with the Roku again and I could listen to music.