I finished a fresh install of GP 2015 and GP 2015 web client. All services are running and Windows Firewall is turned off. When I attempt to log into the web client I get the "A problem occurred creating a session" message.
I am logged in as one of the web client admins and I have added this user to the GPWebClientUsers group in AD. In GP I have updated the GP user to this domain user. What else can I check? There are no messages in the Event Viewer.