Account Upgrade Notification sent in place of Prompt to Complete Registration

Hi. I’ve been setting this plugin up on my site. I’m getting a problem (using paypal subscription) where when someone completes the paypal subscription screen with paypal, they’re sent an ‘account update notification’ not the ‘prompt to complete registration’ email, so they cannot complete the registration process. I’ve been checking everything and I can’t see any reason for this. I’m not changed any php code or added any hooks etc. The plugin is as downloaded. Can anyone help? Many thanks, David