My domain is: http://nodedokku.tk
I ran this command: dokku letsencrypt myApp
It produced this output: listening on: http://0.0.0.0:80/
2018-10-10 20:47:13,374:INFO:main:1211: Generating new account key
2018-10-10 20:47:15,696:WARNING:main:1303: nodedokku.tk was not successfully self-verified. CA is likely to fail as well!
2018-10-10 20:47:15,903:INFO:main:1313: Generating new certificate private key
2018-10-10 20:47:17,069:ERROR:main:1271: CA marked some of the authorizations as invalid, which likely means it could not access http://example.com/.well-known/acme-challenge/X. Did you set correct path in -d example.com:path or --default_root? Is there a warning log entry about unsuccessful self-verification? Are all your domains accessible from the internet? Failing authorizations: https://acme-v01.api.letsencrypt.org/acme/authz/ptm5fXvxHtj7UJl-TtW50E1U6QhbH7SL_9CKg4cYf48
Challenge validation has failed, see error log.
My web server is (include version): Digital Ocean
The operating system my web server runs on is (include version): CentOS Linux release 7.5.1804 (Core)
My hosting provider, if applicable, is: https://my.freenom.com
I can login to a root shell on my machine (yes or no, or I don’t know): yes
I’m using a control panel to manage my site (no, or provide the name and version of the control panel): no