Only ONE user is getting the following:

Login was unsuccessful! - Validation Failed : The status code of the Response was not Success, was Requester => InvalidNameIDPolicy

Everyone else can login via SSO just fine and has been able for the past year. We're using ADFS and FD is the only app using it. 

I tried the support chat with no success, no guidance, no meaningful path to troubleshoot, only general stuff like "it must be xxxx"

Well I need to see what FD sees on SSO attempt for that user. How can I do that?

Said user can authenticate via ADFS test just fine using the usual ADFS testing URL: https://xxx.xx/adfs/ls/IdpInitiatedSignon.aspx