Hi Debbie Could be a combination of a number of things.
Firstly is GST calculating on your entries. If it is not, then you have in your Preferences you don't have track tax turned on.
Failing that, go to Lists, Tax Item List. What Account is showing for say GST, is it Tax Payable.
If not, then that could be your problem.
Go to Suppliers List, highlight Australian Taxation Office, Edit Supplier, Click on Tax Agency Tab, is Tax Payable showing for the account to track tax on Purchases and Sales. If not that would possibly be the problem.