GST Disappearing on Share Transactions (buying & selling)

Hi everyone,
I am using Reckon Accounts Personal Plus 2017. When I buy or sell shares I enter them via "investing", then under "enter transactions" I select the relevant transaction type. In entering the transaction I have been entering the number of shares, price paid, commission & the GST on commission. When I look up the security afterwards, I find the transaction I have entered then has the GST amount no longer there? Further, when I run reports showing the transactions for buying & selling there is a GST column however it is empty (has all "0's"). I have also been back into the transaction to edit it & re enter the GST however the GST amount disappears again when I look up the transaction. Prior to rolling from 2016 reckon to 2017 reckon I don't believe this happened. Any light anyone can shed on this issue would be greatly appreciated as its driving me nuts! Thank you