If users of a sales organization are not able to schedule appointments, on the sales organization page go to Company Settings > Appointment Types and ensure that there are available appointment types.
If there are appointment types, but a user still cannot schedule, check the settings for the appointment type they are trying to schedule. Appointments can be restricted to certain user roles, so ensure the user has the appropriate role.
Appointment Types that are set up for the EPC do not transfer to a Sales Organization. They will need to be recreated in the Sales Organization settings by a Company Admin.