@_elena still gives me "503 Remote SSL certificate could not be verified". Would seem to be an SSL‌ certificate problem, but I'm not sure. If I try on the command line
$ GET https://elenarossini.com/.well-known/webfinger?resource=acct:ele@elenarossini.com

I get a JSON that looks correct, even though it has Content-Type: application/octet-stream (I wold expect some dialect of application/json)