Hi there, Killian. I can provide you with some information on what's the reason why there's no match showing on your invoice in QuickBooks Online (QBO).

There are a couple of reasons why some transactions can't find their match from existing records:

• The amounts or dates don't match.
• The transaction is older than six months.
• The bank account on the payment isn't the same as the bank where the match is located.
• The payment has already been reconciled.
• The transaction matched another transaction. 
• Multiple currencies are involved, and the exchange rate has shifted significantly, making the amounts very different.

Furthermore, matching your invoices in QBO will show a suggested match. However, since it's not showing when matching, you can consider looking for another match invoice.

In addition, you can refer to this article to learn how to reconcile an account in QBO: Reconcile an account in QBO.

Comment on the post if you still have concerns about matching invoices in QBO. I'm always here to help.