Online Appointment in Singapore & Visit Venue for China visa application

Hi there, I am preparing the necessary documents for visa application to China. After entering the fields on the online appointment, it shows 'Date not available' in the field: Please Select a Month. There is also a statement: This month there are no appointment time. I am not able to proceed any further, as there is not any field on web page that allows entry. What should I do next to obtain an appointment?
Also, should I be visiting the office at 150 Tanglin Road? or the application center at 22 Malacca Street for my visa application? Thank you.