It should take a few days maximally, but it takes a few hours mostly. It just depends how fast PayPal sends me notification about incoming payment, some notifications take longer than others although the payment is already marked as finished.
I would check the spam folder at first, then I would check your PayPal details. I noticed that many of the "I can't login" complaints come from users who tries to fill in the login e-mail/zip that does not match their PayPal account.