This error will appear, if one of the customer defined in InLattice has been made Inactive or Deleted from QuickBooks. It means that the customer id is present in InLattice and it does not exist in QB file.

To resolve this problem, please follow these steps:

1. Login to InLattice
2. Go to Settings > QB Interface
3. Click On Refresh Customer list. (This will upload the late Customer List from QB to InLattice)
4. Go to Settings > Edit User
5. One of the customer row should have error in “Acct Pkg Customer Name” column. 
6. Deleted this row (This will remove the customer name from InLattice)

7. Click on Import Invoices

If you still have problem importing the invoices, please send the error.log file in C:\Program Files\Infonics\Inlattice folder. That should have more info on the customer account causing this issue.