I'm trying to build multisite using ProSite. I've registered business and personal sandbox accounts for Paypal, entered sandbox API credentials in the ProSites settings panel, Changed IPN address to the one I had in the settings page. However, when I try to pay for the premium level I only get a blank page in return.
You can register at stronademo.waw.pl/wp-signup.php and see for yourself.
Any idea why it's happening?
Edit. I've just checked that when I switch to Live Mode with sandbox credentials I get redirected just fine. Odd.