Version 1.7 and above of X-ATC-Chatter has a menu item named Check for Updates. You can use this to see if any audio clips have been added or removed from the master collection and you can download them with this function. However, if you need to reinstall the entire product from scratch continue to read the remainder of this FAQ.
If you purchased X-ATC-Chatter from the X-Plane.org store you just need to log into your store account and go to the download page for the X-ATC-Chatter order.
If you purchased X-ATC-Chatter here on the Stick and Rudder Studios website you would have been mailed a Gumroad receipt to your email address. That receipt contains a “View Product” link that you can use to download the product again.
If you lost your receipt you should be able to retrieve it from your Gumroad library https://gumroad.com/library if you had created one. You can also obtain a duplicate receipt here: https://gumroad.com/charge
As a last resort Gumroad can resend your receipt. Simply contact Gumroad at Support@Gumroad.com. Please note that it may take a day to respond to your email depending on your time zone.