Items received to be Invoiced

I have a few invoices to be posted.  Some of these are for items received in 2015, but I am just now getting time to invoice them. 

I go to Purchases/Supplier Invoices/Enter Supplier Name/Enter Supplier's Ref/Enter Date.  The due date should change to 30 days from the date I entered (the account is set up as Net 30 Days).  But the due date doesn't change now.

I have tried changing it to where it should be and leaving it as it is.

Then I add the items I want to invoice and press Enter Invoice, but nothing happens.  It should take me to the next screen, noting that the invoice has been processed.  I can then view the invoice, the GL journal entry and other options.

I haven't made any changes to this supplier or any others.  I have been able to enter invoices for other suppliers without any problems.

Can you help with this problem?

Thank you.