Knif configuration -i ERROR (Service temporarily unavailable)


Hi all,

I am totally a new user of Chef.
Would someone help me out with the following problem ?
Thank you in advance!

I follow the steps of page of Chef, (
Chef-sever 11 and chefdk (including knife tool and chef client) tool are installed succefully.
However when I finished the
chef-server-ctl reconfigure and chef-server-ctl test (no errors)
and start to
knife configure -i on my workstation.

I met a error as follows: (attached in the end of mail).
It seems that service could not be found from the Chef server.
Ping the chef server hostname and Chef server (nginx) also listen the port of 443 for HTTPS.
Furthermore all the services are running on the Chef server normally.
[And I don’t quite understand the message from chef-server-ctl tail]
Do I miss some configuration for Chef server?
Thank you very much indeed!

ERROR: Service temporarily unavailable
/opt/chefdk/embedded/lib/ruby/2.1.0/net/http/response.rb:325:in stream_check': undefined methodclosed?’ for nil:NilClass (NoMethodError)
from /opt/chefdk/embedded/lib/ruby/2.1.0/net/http/response.rb:199:in read_body' from /opt/chefdk/embedded/lib/ruby/2.1.0/net/http/response.rb:226:inbody’
from /opt/chefdk/embedded/apps/chef/lib/chef/knife.rb:573:in rescue in format_rest_error' from /opt/chefdk/embedded/apps/chef/lib/chef/knife.rb:571:informat_rest_error’
from /opt/chefdk/embedded/apps/chef/lib/chef/knife.rb:551:in humanize_http_exception' from /opt/chefdk/embedded/apps/chef/lib/chef/knife.rb:508:inhumanize_exception’
from /opt/chefdk/embedded/apps/chef/lib/chef/knife.rb:499:in rescue in run_with_pretty_exceptions' from /opt/chefdk/embedded/apps/chef/lib/chef/knife.rb:487:inrun_with_pretty_exceptions’
from /opt/chefdk/embedded/apps/chef/lib/chef/knife.rb:174:in run' from /opt/chefdk/embedded/apps/chef/lib/chef/application/knife.rb:139:inrun’
from /opt/chefdk/embedded/apps/chef/bin/knife:25:in <top (required)>' from /opt/chefdk/bin/knife:34:inload’
from /opt/chefdk/bin/knife:34:in `’

Thank you very much indeed!
Best regards,