Registration not working?

I’ve installed the Leaky paywall plug-in (latest version on a website running the latest release of WordPress) and followed all the install instructions.

The paywall works fine, as per the settings I’ve created, but when subscribing, the payment process completes via Paypal, but completely bypasses any registration process on the website, so the user pays the charge, but ends up without a username or password to access what they’ve paid for.

Where am I going wrong?