It sounds like you may have sorted the customer's transaction list by date, with the oldest invoices displaying first. In order to fix this, try these steps:
Sorting in the customer transaction list
From QuickBooks Online, navigate to the Sales tab and the Customers section.
Click the name of the customer whose invoices are displaying in reverse order.
On the column header above Date, click to sort it.
This brief video example demonstrates the above instructions:
We also offer a guide on sorting columns in QBO that you may find helpful. Please keep in touch with me here should you need any further assistance, the Community is always available to serve you. Thanks for reaching out and take care.