Choose the level of the Pro site plan doesn't run

Hello,

I am testing Pro Sites to create my project.
I have this page : http://prosites.renaisens.fr/pro-site/ with the 3 levels.
When I click on the Choose this plan button nothing happens.
The choosen level is not selected.
And When I click on the PayPal button I have a problem else.

How can I fix it ?

Thanks
Pending your reply.
Regards
Ludovic