Event ID 393 - The federation server proxy could not establish a trust with the Federation Service https://docs.microsoft.com/en-us/previous-versions/windows/it-pro/windows-server-2012-R2-and-2012/dn584107(v=ws.11)?redirectedfrom=MSDN https://social.technet.microsoft.com/Forums/windowsserver/en-US/home?forum=ADFS ISSUE: We are performing a brand new deployment of Web Application proxy role on a Windows Server 2012 R2 machine. The Application Proxy Server is in a workgroup machine, while the ADFS server is running on a domain-joined windows 2012 R2 server. For information on the installation pre-requisites and steps, I would suggest you to review the TechNet documentation available here. Now back to the issue,we took the PowerShell approach to install the Web application Proxy role. Install –WebapplicationProxy –certificateThumbprint <Hashvalue> FederationServicename <name of the adfsservice > When we ran this command let, we encountered the follo...