Also – is the file a conversion or a file that you have created?
Do you use Multi-currency?
Can you work out the date when the imbalance occurred?
That means selecting date options – it will balance ok and then extend out the date to when it doesn’t balance..
through a process of elimination […]

Resolution for 'AU issue: 'AU Trial balance that is not balance' available: Yes.

The AU issue or error code is a known issue in Quickbooks Online (QBO) and/or Quickbooks. Support for this issue is available either by self-service or paid support options. Experts are available to resolve your Quickbooks issue to ensure minimal downtime and continue running your business. First try to resolve the AU issue yourself by looking for a resolution described in the article. If it is a complex AU issue or you are unable to solve the issue, you may contact us by clicking here or by using other AU support options.

For more information about resolving issues related to AU in Quickbooks/QBO or to get support for the issue 'AU Trial balance that is not balance', click the link below: