Popup onclick rule only works once

I'm trying to use the Popup onclick rule to prompt people to register on my site, however the popup only ever shows once.

If I click the link, see the popup and then close it using the X, I cannot then click any of the links again and see the popup again.

The page on my dev site is here http://www.webmolecms.co.uk/trillion/investment-projects/bnrg-gorse

The following links should trigger the pop up:
Test
Meet the team
Benefits and risks
Technology

The following rules are set:

a.login-or-register as the tag to initiate the popup.

Show if user is not logged in

'Regular close button acts as "Never see this message again" link' is unchecked

How can I make the popup appear any time the link is clicked?

Thanks