@_elena it could be a problem of your webserver config, it seems to either not generate the webfinger path properly or the hoster/config blocks it. This should return JSON https://elenarossini.com/.well-known/webfinger?resource=acct:ele@elenarossini.com
You can try to regenerate the rewrite rules: Go to the permalinks page and press "save", you do not have to change something. Then re-check the URL above.