The Signups page is powered by Registrations, so any changes that need to be made to the Signups page have to be made in Registrations. Go to Registrations to manage your account or see who your Registrations Administrators are to gain access.
This is what the Signups page looks like on Church Center. You can manage this information from Registrations.
If an event is not showing up, make sure the visibility is set to Published.