Solution: Client with the currently selected authenticator does not support any combination of challenges that will satisfy the CA

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I'm using nginx and trying like this:
certbot --authenticator standalone --installer nginx -d mysite.com --pre-hook "service nginx stop" --post-hook "service nginx start"
certbot fails with a TIMEOUT trying to fetch:

IMPORTANT NOTES:

  • The following errors were reported by the server:

    Domain: mysite.com
    Type: connection
    Detail: Fetching
    http://mysite.com/.well-known/acme-challenge/:
    Timeout

    To fix these errors, please make sure that your domain name was
    entered correctly and the DNS A/AAAA record(s) for that domain
    contain(s) the right IP address. Additionally, please check that
    your computer has a publicly routable IP address and that no
    firewalls are preventing the server from communicating with the
    client. If you're using the webroot plugin, you should also verify
    that you are serving files from the webroot path you provided.

I'm already read the post on official forum but no of both methods doesn't work. It's just stacking on:

Cleaning up challenges

or giving TIMEOUT ERROR

Is there any way around this yet?
Is there anything outsiders can do to help?

PS: Thanks to all of you for your hard work and I really appreciate you staying on top of the security issues...