In order to access pages from your hosted Atlassion Confluence on GNU Emacs via confluence-el mode, the confluence-url variable should be set thusly (assuming it’s placed within custom-set-variables arguments):

 '(confluence-url "https://<hosted-site>/wiki/rpc/xmlrpc")

Where <hosted-site> is probably somewhere.atlassian.net. Or not. At least in my experience, 100% of the cases (actually a case) it was that way.