Hi there, James. This happens because the transition to Modern reporting has already been rolled out to several users as QuickBooks Online advances into a new era.
We recognize the Sort button from the Classic report is a key feature for your workflow. Please know that Intuit is using customer feedback to ensure the Modern reports include these essential features before the Classic versions are fully retired. Since this rollout is happening in stages, some accounts now only have access to the Modern report.
In the meantime, have you tried running the Accounts Receivable Ageing Detail report? It currently offers the granular, column-based sorting that the Summary version is still transitioning toward.
If you have any further questions, please let us know in the comments below.
