After ordering and paying you will get a confirmation email with the order number and other details.
It can be that the mail got in your spam folder or that your email provider had it blocked.
There is nothing avast can do about that.
You don't get a invoice, you get a confirmation.
Invoice means a bill that you have to pay.
You can check your order status at:
https://www.avast.com/find-order80 licenses?
You have 80 systems?
That does not sound like you are a private person but need to get a corporate license.
And there is no need/reason at all to post multiple times about the same thing.