Gmail and sending invoices

We just recently changed up from using BV Delta to Sage BusinessVision.

I just got the email setup working for sending invoices, etc via our Gmail account.

The question I have, is that the OLD invoices imported into the system do not seem to want to be emailed, as in it opens up a VIEW screen of the invoice instead of sending it via e-mail.

And for what ever reason, a customer that has invoices in our system back to 1992, I can not seem to send any invoice via email, even though I have the email field filled in in the customer information section. Even an invoice created earlier today does not email (icon to send via email is grayed out).

Please bear with me, as we have only set a few customers up with emails so that we can email invoices, more of our more frequent customers will be changed over.