Tiled Landscape "import" is remaining grayed out

I’m attempting to import a tiled landscape I created using L3DT, and while I can select the .r16 files, the import window remains blank as though I still haven’t imported anything. Any ideas as to what the problem might be? On a side note, does anyone know how to export weight maps from L3DT?

I was trying to follow this guide as best as I could with the different software, but am sure I likely messed up somewhere.

To clarify, I don’t have any issues importing a single landscape file; it’s only when attempting to import the tiled landscapes.