The process of verifying the paid signup is manual I believe, so it may take a day or so before your login is live. If it's still not active for you in 24 hours I'd suggest contacting one of the site admin's in stickymail that are listed in the top right of each forum group here [webmasterworld.com]
After years of participating, I finally subscribed to the paid section of WW. But I was expecting my login to work immediately, and kind of bummed that it didn't
My suggestion is to set up an email to new paid subscribers letting them know the process as well as when they can have access to the paid section. This way, they know what to expect. My instinctive reaction was to go back to Paypal to cancel the subscription because I didn't think it worked.