If you create a new Service from the "Create New: Service" link in the Services & Activity section of the Customer Profile screen, it will not immediately be visible in this section.

The reason for this is that this method of service creation does not provide a method for adding products to the service during the creation process. If a service does not have a product assigned to it, the service will be in a "Disconnected" status until one is assigned. To see disconnected services within the Services & Activity section, you must check the Include Inactive Services box located at the top of this section. 

Once made visible, you can go to Options > Add Service to add a Product to the service. Afterwards, the service will always display whether the Include Inactive Services box is checked or not.