I have an issue where I can not approve or reject an approval. Initially I thought there was something wrong with my MPR's (see https://social.technet.microsoft.com/Forums/en-US/b24c7776-d5bc-4412-b4d2-a59e48f864a5/unable-to-approve-request?forum=ilm2) but it turns out it is an issue when using HTTPS to the FIM portal.

What happens is that someone can go into the page to approve / reject their request but they can't click on the approve/reject icon. The icon's are there but nothing happens.
They do this using a HTTPS link (e.g. https://identityserver.com).

When I do this from the local FIM server using thier account it works.

If I disable the HTTP-to-HTTPS rewrite rule on the FIM server and  use e.g. http://servername the approve/reject buttons work.

The FIM portal has a binding for https to hostname https://identityserver.com and port 443. This all seems to work as you can get to the FIM portal from external but as I said, some things don't seem to work.

I setup an alternate access mapping in Sharepoint as follows:
INternal URL: https://identityserver.com
Zone: Custom
Public URL for zone: https://identityserver.com

What am I missing???