Remote checks have failed too many times

hi,

the api URL is accessible

curl -SI https://api.graylog.com

HTTP/1.1 200 OK
Server: Cowboy
Connection: keep-alive
Content-Type: text/plain
Content-Length: 133
Via: 1.1 vegur

This is a fresh installation and I have not changed the default path.
How can I better investigate this issue?