I'm not sure why your post title mentions "authentication" when you have no evidence at all that authentication is the cause of the failure. It's never a good idea to make evidence-free decisions like that, since it's likely to make you look in the wrong place for the actual problem.
Anyway you should start with the only piece of evidence you do have, the small log file at the end of your post. Pay particular attention to this line:
See the server log for details.
because it tells you how to find more information about the actual problem.
Then set that XML file back to the previous version from your source control which you know works. Use that to start Tomcat, and then look for the log files. Make sure you know where to find them, so the next time an error message tells you to look at them, you know where they are.
Happiness is not a goal ... it's a by-product of a life well lived - Eleanor Roosevelt. Tiny ad: