A note on why the answer is always the same
Whatever you type, this page says the same thing: if that address has a licence, the download is on its way. It does not tell you whether the address was found. That is on purpose — a form that answered “no such customer” would let anybody type in an email address and find out whether that person is a customer of ours, and that is not information we are entitled to hand out.
If nothing arrives
Check the spam folder first. A plain email with a single download link in it is close to the platonic ideal of what a spam filter is looking for, and it catches ours more often than we would like.
If it is genuinely not there, the most common cause is that the purchase used a different address than the one you are trying — a work address, or a personal one, or an accountant's. Write to us with anything you do have, including the receipt or the card's last four digits, and we will match it up. Support
What to do with it
Download the file and upload it under Plugins → Add New → Upload Plugin. Your licence is already inside it, so there is nothing to paste anywhere and nothing to keep somewhere safe. If you are moving the site to a new domain, nothing needs doing at all — a move is not a second site under our terms, and your installation keeps the same identity across the move. If a site is ever still counted against you, write to us and we will clear it; nothing is locked while that is sorted out.