My customer did not receive the invoice

The status Sent means the number is final and the pdf is ready. That is not the same as: an email actually went out.

This is what may be going on

There is no email address on the customer.: Without an email address the invoice does get a number and the pdf is created, but nothing goes out. Go to Contacts, open the customer and add the email address. Then click Resend on the invoice; the invoice number stays the same.
You used Mark as sent instead of Send.: That choice deliberately sets the invoice to sent without emailing it, for instance for postal mail or for an invoice you carried over from your old package. If you want to email it after all, click Resend.
The email was sent but ended up in the spam folder.: Ask your customer to check their junk mail and to add the sender to their contacts. If your own domain has not been verified yet, the email goes out from a TELMAAR address with your address as the reply-to address; with some mail providers that can land in the spam folder.

Download the pdf through More and then Print and forward it yourself.
Use View as customer to see what your customer sees in the customer portal, and forward that link.
If it stays quiet, the automatic payment reminders pick it up from three days after the due date.

Last checked on 28 August 2026