SAML - Could not verify the provided CSRF token

Following this guide: https://developer.okta.com/code/java/spring_security_saml/

After having added the metadata link to the serverContext.xml and restarting Tomcat, I now see the Okta Start Single Sign on button, but when I click it I get an HTTP Error 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/8.5.55