I send an invoice but does not show as sent.

[levalusa]

This is the second time ( 2 different buyers)  in 2 weeks that I have sent an invoice to a domestic buyer and it appears to go through with no error message but when I go to orders page it just says "send invoice" as an option as if I never sent one. I even tried to send another and same thing happens... all my other sold items have no problem, invoices sent and I await payment.  Any ideas why the invoice shows as not sent.