I have an embedded Survey123 Widget in my Experience Builder application that does not connect when NOT logged into an ArcGIS Online account. When logged out, clicking the survey widget displays a white pop-up window with the text "www.arcgis.com refused to connect."
The widget works exactly as intended when logged into my organization's user account; however, I need the widget to be available to the public.
The survey in Survey123 is set that Everyone (public) can submit to the survey. And submitters can 'add and update records.'
Do you have "only one submission" set in Survey123 under Multiple Submissions? This requires an AGOL sign-in. If I remember correctly, updating of a record requires login control too.