You are allowed to access to several Darknet markets using only the links, it determines the following : inpending buyers and dealers are not allowed to enroll until they will get an alternative URL from an already enlisted user.
Look at https://darkwebonion.com/, it possesses active alternative URL to suggested Darknet marketplaces. You ought to follow these alternative URL in order to get access to the sites.
Whenever there are some problems with an access (links don't work), you ought to lie in wait and check for Deep Web marketplaces alternative links. Keep trying, because few marketplaces shut down and open registrations regularly, based on server load.