Modsecurity Test not working. What to do?

I am running modsecurity on Ubuntu server. I have followed the modsec tutorial step by step.
However when entering or 'a'='a' into my web browser, it redirects to the following page (which ends up being the site homepage, not a 404 error page):
This is not the same as in the example which is:

How can I correct this?

I must have messed up something in the modsecurity config files that I kept overlooking. However, I couldn’t find the exact error. Therefor, my solution was to completely remove modsecurity, and then rebuild and reinstall it, following the modsecurity tutorial from scratch again. This fixed things and can be documented as the solution.