Create proxy not working and doesn't accept google app script url

[Davide]

I have a Google Sheet app with Google Apps Script with its deploy which generated a link https://script.google.com/macros/s/....../exec. I would like to put it on Feedburner, but although it works and it can be seen, on Feedburner it is not accepted, it blocks in the second phase of the creation of the proxy and throws the error "ERROR: Unknown Error".

Is this a known issue?