Is there a report showing all payments made on a customers account that has NOT been matched successfully to an online match after uploading the banking transactions?

Thanks for asking the Community, @eleanor-okeeffe-. I'm your QuickBooks guide today. 

We can generate a report filtered by cleared and uncleared status. Here's how: 

1. Go to the Reports menu.
2. Enter Transaction Detail by Account in the Search field.
3. Select the Date of the report.
4. Filter on "Cleared": Uncleared"
5. Select Run report. 

You can also save your customization so you can use it in the future. See this article for further insights: Memorise reports in QuickBooks Online. 

For future reference, follow the steps to categorise and match online bank transactions in QuickBooks Online.

Get back to this post if you have additional questions. I'm always around to help some more.