The following steps outline the process of matching Items and Importing Invoices from QuickBooks into EDI Engine.

From the Document Navigator in EDI Engine select a Processed PO to invoice

From the Document Navigator:
1) Select Inbound.
2) Select Processed and Ready.
3) Narrow the Date Range.
4) Double Click (anywhere in the first few columns) to open the processed PO you want to invoice.

Make sure the items listed in the PO are Matched to QuickBooks

1) Select the Items tab.
2) Take note of these line items. You will need to make sure they are all matched to QuickBooks before you import invoices.

Open Intuit QuickBooks - Items window to Match Items

Go to:
1) Quickbooks
2) Setup
3) Select Items.

Match Items to QuickBooks

1) Select Show Unmatched.
2) Select each Unmatched Item and do the following:
3) Either search by Item Code or
4) Find the corresponding item in the QuickBooks Items list.
5) Click Match.
Close Quick Books - Items window

Close Purchase Order window

1) Click X to close window.

Import Invoices

From the Document Navigator:
1) Select Outbound.
2) Select Processed and Ready.
3) Narrow the Date Range.
4) Select the Quickbooks tab.
5) Click the Import Outbound Invoices (810/880) button.

Import Invoices

1) Tag the invoices you want to import.
2) Click Load.
Finally, once the invoices are imported from QuickBooks you can Export to EDI as you normally would.
A dialog box will confirm that the invoice(s) were imported successfully or let you know if there were errors.

Checking Processing Logs for errors

If there were errors in the Invoice Import Process, open the most recent Processing Log to view error details. 
1) Select the top entry in the Log Report.
2) Make sure the Only Entries with Errors box is not checked.
3) Click Process.
If you need assistance troubleshooting an error, either copy and paste the contents of the processing log into a support ticket/e-mail or save the notepad file to your desktop and attach it to a support request.

Check out for more information on Processing Logs.