I've been setting up ADFS on Windows 2016 (server core) in my home lab for the first time and had some problems near the end.

All the directions I've been following state that to test your ADFS deployment once completed you can go to:

https://<FQDN>/adfs/ls/idpinitiatedsignon

I was able to access the site, BUT was receiving a fairly unhelpful error "An error occurred":

Looking at the ADFS event logs, it stated (in abbreviated form):

Microsoft.IdentityServer.Web.IdPInitiatedSignonPageDisabledException: MSIS7012: An error occurred while processing the request. Contact your administrator for details.

Long story short, apparently there is an ADFS property (EnableIdpInitiatedSignonPage) that by default is set to False.  It took me a while to figure out, hopefully this will help someone else.

To check it, open Powershell and run:

1. Get-AdfsProperties
2. Check to see if EnableIpdInitiatedSignonPage is set to False: 
   
3. If it is, run: Set-AdfsProperties -EnableIdpInitiatedSignonPage $true
4. Test your ADFS web page again (no need to restart): 
   
5. You should be able to sign on now (hopefully).