You are required to access to some amount of Darknet marketplaces only with an urls, which implies a tricky situation : prospective customers and dealers lack the ability to join the market until they will get an alternative URLs from an already registered shopper.
Look at https://darkwebonion.com/, it possesses updated URLs to suggested Deepweb markets. You should go to these alternative link in order to sign up at the sites.
If there are some issues with an access (links don't work), you should hang around and check for Deepweb markets alternative URL. Keep trying, for the reason that some of the markets close and let registrations regularly, due to server load.