Please use this form to send a message: https://www.nch.com.au/support/regcontact.html
Or try CHAT support.
From an NCH FAQ...
"Can I upgrade from a previous version? What is the upgrade policy?
All minor upgrades and bug fixes and some major upgrades are available free. Simply install the new file over the old file.
If we introduce major new features or change the registration system, we may require users to purchase an upgrade.
We guarantee free upgrades for 6 months from date of purchase but in practice we often allow upgrades up to 12 months.
If in doubt back up your old version and just try the new version. If you purchased more than 12 months ago, you will need purchase an upgrade to the current version."