Could not verify the provided CSRF token

Making really good progress with this tutorial.
https://developer.okta.com/code/java/spring_security_sam

Was stuck for a while but realized I needed to do this after Step 2
git checkout rb1.0.4.RELEASE

Also switched to the classic UI to match the example.

However, having added my metadata link to the serverContext.xml and restarting, I now see the Okta Start Single Sign on button, but when I click it I get a 403 , CSRF token error:

HTTP Status 403 - Could not verify the provided CSRF token because your session was not found.

type Status report
message Could not verify the provided CSRF token because your session was not found.
description Access to the specified resource has been forbidden.

Apache Tomcat/7.0.56