After you create a new location, you also have to make sure that you are added as a staff member to the location. Tikkit only shows you the locations that you are assigned to as staff.
You can also set staff users up to be automatically added to any locations as soon as they are created. You should only do this if you actually want a given user to have access to every location; in such cases, this option is a huge time saver.
Learn how to assign staff members to a location, or to give staff members access to all locations.