We understand that 2020 has been a difficult year but we're here to try and make it a little easier for you during tax time. You can search other people's posts, read our articles or ask your own question.
I have experienced the same issue for my client. I was told by ATO (via phone call) that this was because I submitted the form in the old platform but payment has not been made in time to clear out the amount. It can be fixed by deleting the old batch and then re-submit the same amount again for the same period. You should be able to view the details of payment method after submitting in the new platform.