I created a public survey last year, probably with Survey123 Connect 3.9.x, though I don't know for sure. I updated Connect to 3.14 this year, and have updated the survey numerous times. The Edit and Resend function is supposedly enabled:
1) Allow Sent Surveys to be edited is toggled on in the Options tab of Connect.
2) In Survey123.arcgis.com, I have enabled submitters with Add/Update/Delete permissions, and it's set to Public.
However, unlike last year, anonymous editors are NOT able to Edit and resend their existing surveys from the Sent folder. THe survey gets stuck in the Outbox with a non-specific error message. When I sign in, as the owner I can edit and resend surveys I created both anonymously and while signed in on that device.
The behavior seems specific to this Survey, since another one I created last year around the same time and have also been updating does allow anonymous editing.