I am trying to setup IdP initiated SSO on Windows Server 2016. I have configured the Relying party trust and the claim rules as well. I enabled the IdP Sign on page following - https://docs.microsoft.com/en-us/windows-server/identity/ad-fs/troubleshooting/ad-fs-tshoot-initiatedsignon
Now, when I go to a machine and try to access https://<ADFS_HOSTNAME>/adfs/ls/idpinitiatedsignon.htm, I get PR_CONNECT_RESET_ERROR on Firefox (and similar errors on other browsers). I took a pcap and I see that the Windows server is not responding to the Client Hello sent by a Client. Things I have already checked:
- ADFS Service is running
- From a client machine in the same network I can telnet to the Windows Server on port 443
However, the page won't load in order for me to select a service and login there. I have not configured this Windows Server 2016 myself, I am using this to setup IdP initiated SSO and I think that I am missing some prerequisites so that my AD Server can accept a IDP SSO connection (or a HTTPS connection). Please advise what else can be checked, I am happy to share any other info required.