Do you have 30 day after the end of the month terms for your customers?
If these are January invoices, Infusion cannot assign the date 30 February to the invoices so they remain blank.
You will need to manually update these invoices to the due date of 28 February. Open the invoice and click in the date field, then tab out of it to allow Infusion to calculate 28 February as the due date.
If your Pending Invoice list is too large to manually process this Support Staff may be able to update this for you - please be aware of your Customer’s Terms and how many do not have the 30 days after EOM terms as this will affect the time it takes to process this.