I have no idea why.  Everything appears to be set up properly.  Pass Thru account was created successfully, I get "success" messages when enabling, but when I visit the page, I get an NTLM failed message and am forced to sign in.  When signing in, I can use my domain credentials to successfully sign in.

I see some "Access Denied" errors in the logs, but I have no idea what access has been denied, the logs are not very clear.  I've zipped up the logs folder and am attaching them here.  This is the most recent version of Service Desk available.