Dimension Keeper:
First, I'll send you to the waiting room, a safe space we created. While there, speak with the Keeper of the Gap. He'll allow you to enter the dimension gap.
However, they are classified based on the place that they manage.
Level 30's are managed by Recruits, Level 40's by Privates, Level 50's by Officers, Level 60's by Captains, Level 70's by Commanders, and the higher levels by Heroes. Don't forget this, and visit a keeper of the gap appropriate for your level. Well, good luck to you.