Sometimes the orders are importing to the system in a wrong way and the users need to remove the invoice that was created against the order. In that scenario first the unnecessary invoice needs to be removed from the A/C system. Ones it is removed open the order, Go to Shipments\Invoices tab; right click on the invoice that needs to be removed and select the option "Remove"
Please see below;
Please contact The Order Exchange Support if there are any further issues on this.