ACCA has reiterated that there is availability for September exam and you should be able to book your chosen exam centre. There have been some changes to the system – candidates need to enter the specific exam date to show the centre availability.
Go onto your MyACCA account http://accagobal.com/myacca. You must not use any previous links you have been used.
If you are still experiencing issues contact the ACCA immediately via email at firstname.lastname@example.org/uk/en/footertoolbar/contact-us.html