In my case, i was having issues when i tried to access to the backend using http. Sitefinity redirected me to https and when i typed my credentials, i was getting the error: Missing configuration for the requesting relying party https://site.domain.com
I added the security token issues and it didnt fixed. What have to do was:
in web.config, i changed the wsfederation line:
<wsFederation passiveRedirectEnabled="true" issuer=http://localhost realm=https://Sitefinityxxxx.domain.com requireHttps="true" />
<cookieHandler requireSsl="false" />
I have to add the S to http and use the fqdn of the server. After this change, i was able to login with http redirection and https.