XOG Login is failing in a new install or upgrade, but was working previously. In "verbose" logging mode the error is seen:
HTTP Error: Status-Code: 400: null
ca-log shows errors like:
niku.xog (clarity:none:none:none) XOG POST failed
Release : 15.8.1
Component : CA PPM APPLICATION
Problem is caused due to the Clarity application on the server being unable to write to the temp directory on the server. As a part of the XOG process, files are saved into the temp directory and then processed.
In a Linux installation a specific user account would be used to start the Clarity services. Ensure this account has the ability to write to the system's temp directory.