If you have found that you have invoices missing from an exported batch in your ERP system (Sage, Dimensions etc.) then it is likely caused by a drop in connection while exporting. There is a way you can check this.
First, remove the failed invoices from the exported batch, you can find details of how to do this in the first half of the knowledge article 'here' .
Create a new batch with only the affected invoices, export these again to your ERP system
Should this now work successfully, this means it was caused by a connection issue and this will need looking into from your IT department. For instance, the disk space is nearly full on the server and needs increasing. There are a couple of workarounds that can be actioned whilst the investigation takes place:
Create batches in smaller chunks of invoices
Try and export from another PC in your organisation. It could be that your connection issues only affect certain terminals.
Another possible scenario is that the invoices were altered before the export. For example, you can delete individual invoices from the batches and the audit trail shows when a export was actioned, but not when it was altered. The batch and the invoice are not directly linked. So a batch could have been altered with the invoice removed and no audit of it being altered written.