If you have your QBO connected but invoices are not showing up in QuickBooks, it is possible that while the integration is turned on under Company > Settings > General > Integrations, you do not have each specific client connected.
You will need to click on each green QB Connect button (seen below) and link to the existing customer in QBO. If it’s a new customer not in QBO, you'll need to specify to create a new client. You will only have to do this once for each customer.
A customer who does not have QBO connected will show that QBO is not connected from their Customer Profile, as seen below.
They will also show a green connect button on the Invoicing and Job Records, as seen below
If the customer is already connected to QBO, and invoices are still not visible, make sure they are connected to the correct QBO customer. They may be connected to a duplicate QBO customer by accident. If they are connected to the wrong account, here’s our guide to connecting them to the correct QBO customer.