[TYPO3-project-seminars] Users are not redirected to the thank you page after registration

[Brian Bendtsen]

Hi

I have created a registration page and inside this a thank you page like 
the manual says. On my root TS setup I have this:
plugin.tx_seminars_pi1.thankYouAfterRegistrationPID = 19
where 19 is the pid of my thank you page.

But my registration page (20) is called instead telling the user they 
are already registered for this event.

Do I need to do anything else for this to work?

/Brian Bendtsen