Hello,
I had this pop up yesterday with two surveys. After some troubleshooting, I found a bug: A group with table-list appearance AND a non-select_one/select_multiple question (e.g., a note or text) as the first element inside that table-list causes the survey to give this error. The survey is still visible and accessible in Portal (and I would assume AGO).
This bug has been logged with Esri, and a fix will (presumably) be worked on and deployed sometime in the future.
EDIT: For clarification, this comment is in response to another more recent comment. The original reason this particular thread was started was for a different bug which has long since been resolved. However, the error message is generic, so there are many reasons why you could be seeing "The survey is not accessible or does not exist."
EDIT2: Logged as BUG-000160874