OK, so from the lamp device page (child, as it is the only one with set level), I opened the device logs in another window (cntl-click). I then set the level in the device page to (0), click the button, and nothing.
I View the device log I opened in the previous step and it is only populated with info from the sunset ramp-up to 50% - nothing further. The logging shows as being on "device 5". No error is present, no event, last entry was at 2022-06-14 20:10:54.261 when it reached the target 50%. I even went back to the device page and deleted/retyped the level to (0) and clicked the button again = still nothing and no new log at all.
I also went to the logs from the main sidebar menu (live logs, ) and there I see two errors for "Device 4" Tiffany lamp. Same error: Exception when sending: status code: 400, reason phrase: Bad Request. Please check your device settings.
Hope this helps, still learning the nomenclature for the various areas of this(these) environment(s).