Your Membership is working just fine, young Wizard. Wizard101 is a story driven game. You must complete the story line quests to progress. You are required to complete tasks in Firecat Alley, Cyclops Lane and Triton Avenue before your Wizard is strong enough for the next world. I would also suggest you complete Colossus Boulevard before you venture into Krokotopia as it will teach you how to manage more than one foe at a time.
Once you have completed all your required assignments in Wizard City, Merle Ambrose will ask you to investigate Krokotopia.
Once you have been given that quest, you can access the Spiral door by entering Bartleby the World Tree.