You will have to change to using the Google API for your web App (UI) if it is a must.
It is against the Legal agreements outlined with Google to use Google Street view without using the Google API.
This widget was built years ago and was stripped due to this legal issue.
Some light reading:
https://community.esri.com/docs/DOC-2991
We need street view in our AGOL apps so that our engineering staff can view areas around projects.
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