I got it working by updating the Chromecast and all its apps, factory
resetting and then setting up again manually with the remote, not the
Home app. In that order. Tedious but now works.
Yep. Same here. 75" Samsung 4K TV and brand new, fully updated,
Chromecast 4K and selecting ‘Add device’ under ‘Set up remote buttons’
spins for a second then takes me straight back to the previous menu.
Have updated the Android TV Infrared Service. ...