You are able to log into several Deep Web marketplaces using only the alternative URLs, this implies a tricky situation : new vendees and vendors can't sign up until they will get an alternative URLs from an already joined customer.
Those can be found at /darkwebonion.com/, it has new alternative URL to all of the Deepweb marketplaces. You ought to follow these alternative URLs to register on the sites.
Whenever there are some problems with an access,for example, links won’t work, you should wait and check for Deep Web marketplaces alternative links. Keep trying, as few markets close and open signing up regularly, based on server load.