Terrain Presets + Profiles, are now in .XMP format, which is standard for Lightroom 7.3 , and are installed in a different manner versus the previous .LRTEMPLATE files. Please start by Downloading our Install Guide HERE. Option B in the guide is usually the simplest method for installing the new presets/profiles.
The Terrain Presets/Profiles require Ver. 7.3 or newer. Please verify that you have the correct version, as the new profiles will only work with Lightroom 7.3 or newer. You can find your version information in Lightroom by selecting (MAC= Lightroom > About Adobe Photoshop Lightroom Classic CC ::: PC= Help > About Adobe Photoshop Lightroom Classic CC)
The video below will also take you through the install process.