The demo does not go to any backend. The URL is there to only match if it's created with same destination. Please create an incident and someone can take a look.
The issue is definitely in your onboarding URL and branded settings. They are not correct or not available, and hence, you are getting 404. Reverify if they are accurate. You can copy paste the redirect url into a browser and check if it's reachable.
Hi,This online search is available if you have CA_ONLINE_SEARCH parameter enabled from the configuration. Please enable that and it should be available.