'Web Administrator' Responibility is not required for every user. As per my observations, you need to add one more responsibility (ex: Web Anonymous User) and you can log into SSA.
make sure that pricelist added to that user .
'Web Administrator' responsibility is assigned to a user to change Site settings for SSA.
A normal user is assigned responsibilty "Web Registered User".A registered user is associated with an
individual account and profile. A B2C registered user is responsible for viewing, analyzing, and
paying for his own account. In addition to the items available to anonymous users, registered
users can manage their profiles, check out merchandise, and place orders.
An anonymous user is not associated with an account or profile, or with any
organization. An anonymous user could be a user who has not yet registered, or a registered
user who has not yet logged in.
Documentation is provided by Oracle for the same.
Feel free to contact me for further clarification's.