Error in calculating the payment amount when lodging BAS

Hi!

I am experiencing an error in MYOB like when you input amount (when lodging BAS), it does not automatically calculate the amount to be paid or refunded. I am using a new computer and suddenly it was not working anymore. I tried to used my old computer with the same MYOB account and it works. Hope you can help me. Thanks. Badly need this as it is BAS season.