Please check the path assigned in your DPSSQLConfig, and that the invoices you are picking up are being saved to the same folder in the path. You can check the path saved in the DPSSQLConfig, by following the below steps:
Enter the DPSSQLConfig.
Select Accounts tab.
Select Accounts Settings.
Under Enable Invoice Documents add a folder of your choice which is where you will be holding all of you invoices. Please consider if this should be a local or shared drive.
Click Save.